This is a complete, free book detailing how to build your own AK pistol from scratch in .22 rimfire, 7.62x25, 9mm, or any pistol cartridge.
24HR-AK47
Friday, February 22, 2013
Blowback Autoloader Design
Blowback is a system of operation for self-loading firearms that obtains power from the motion of the cartridge case as it is pushed to the rear by expanding gases created by the ignition of the propellant charge.[1]
Several types of blowback systems exist within this broad principle of operation, each distinguished by the level of energy derived through the blowback principle and the methods utilized in controlling bolt movement. In most actions utilizing blowback operation, the breech is not mechanically locked at the time of firing: the inertia of the bolt and recoil spring(s), relative to the weight of the bullet, delays opening of the breech until the bullet has left the barrel.[2] A few locked breech designs use a form of blowback (example: primer actuation) to perform the unlocking function.
Other operating principles for self-loading firearms include gas operation, recoil operation, Gatling, and chain. The blowback principle may be considered a simplified form of gas operation, since the cartridge case behaves like a piston driven by the powder gases.[1]
What is common to all blowback systems is that the cartridge case must move under the direct action of the powder pressure, therefore any gun in which the bolt is not rigidly locked and permitted to move while there remains powder pressure in the chamber will undergo a degree of blowback action.[3] The energy from the burnt gases appears in the form of kinetic energy transmitted to the bolt mechanism, which is controlled and used to operate the firearm's operation cycle. The extent to which blowback is employed largely depends on the manner used to control the movement of the bolt and the proportion of energy drawn from other systems of operation.[1] It is with how the movement of the bolt is controlled where blowback systems differ. Blowback operation is most often divided into three categories, all using residual pressure to complete the cycle of operation: simple blowback, advanced primer ignition and delayed blowback or retarded blowback.
The Colt Model 1908 Pocket Hammerless is a popular example of a simple blowback pistol chambered in .380 ACP. The resistance provided by the mass of the slide alone is enough to delay opening of the chamber until pressure in the barrel has dropped to a safe level.
The simple (sometimes referred to as the "straight" or "pure") blowback system represents the most basic form of blowback operation and demonstrates the basic principles involved in the blowback cycle.[1] The simple blowback mechanism typically consists of the bolt which rests against the base of the cartridge case and a recoil spring that resists the kinetic energy of the bolt when it is thrown back in recoil and then drives the bolt back forward into firing position.[4]
The cycle begins when the cartridge is fired. Expanding gases from the fired round send the projectile down the barrel and at the same time force the case against the breech face of the bolt, overcoming the inertia of the bolt, resulting in a "blow back" effect. The forces exerted by the powder gases exist for only a relatively brief moment; lingering residual gases continue to act on the case for an even shorter period of time. The breech is kept sealed by the cartridge case until the bullet has left the barrel and gas pressure has dropped to a safe level; the inertia of the bolt mass ensures this.[4] At this point the powder pressure is zero and the force driving the bolt back is also zero, but the case and bolt continue to the rear of their own momentum.[4] As the bolt travels back, the spent cartridge case is extracted and then ejected, and the firing mechanism is cocked while the bolt begins to decelerate against the resistance provided by the recoil or action spring. The bolt eventually reaches a velocity of zero and the kinetic energy from the recoil impulse is now stored in the compressed spring (some energy loss does occur due to friction and the extraction and ejection sequences).[4] The action spring then propels the bolt forward again, which strips a round from the feed system along the way. The bolt carries a new cartridge into the chamber with considerable velocity and the action spring completes its energy transfer just prior to return to battery. The forward velocity is entirely dissipated upon impact with the chamber face.[4]
To remain practical, this system is only suitable for firearms using relatively low pressure cartridges. Pure blowback operation is typically found on semi-automatic, small-caliber pistols, small-bore semi-automatic rifles and submachine guns. Some low-velocity cannon and grenade launchers such as the Mk 19 grenade launcher also use blowback operation.
The barrel of a blowback pistol is generally fixed to the frame and the slide is held against the barrel only by the recoil spring tension. The slide starts to move rearward immediately upon ignition of the primer. As the cartridge moves rearward with the slide, it is extracted from the chamber and typically ejected clear of the firearm. The mass of the slide must be sufficient to hold the breech closed until the bullet exits the barrel and residual pressure is vented from the bore. A cartridge with too high a pressure or a slide with too little mass may cause the cartridge case to extract early, causing a separation or rupture. This generally limits blowback pistol designs to calibers less powerful than 9x19mm Parabellum (.25 ACP, .32 ACP, .380 ACP, 9x18mm Makarov etc.). Any larger and the slide mass starts to become excessive, and therefore few blowback handguns in such calibers exist; the most notable exceptions are simple, inexpensive guns such as those made by Hi-Point Firearms which includes models chambered in .45 ACP, .40 S&W, .380 ACP and 9x19mm Parabellum.[5]
Most simple blowback rifles are chambered for the .22 Long Rifle cartridge. Popular examples include the Marlin Model 60 and the Ruger 10/22. Some blowback rifles or carbines are chambered for pistol cartridges, such as the 9mm Parabellum, .40 S&W and .45 ACP. Examples include the Ruger Police Carbine, Beretta Cx4 Storm, Marlin Camp Carbine and Hi-Point Carbine. There were also a few rifles that chambered cartridges specifically designed for blowback operation. Examples include the Winchester Model 1905, 1907 and 1910. A very unusual blowback rifle was created by fitting the M1903 Springfield rifle with a mechanism called the Pedersen device.
In the API blowback design, the cartridge has not been fully chambered and the bolt is still moving forward when the primer ignited. In a plain blowback design, the propellant gases have to overcome static inertia to accelerate the bolt rearwards to open the breech. In an API blowback, they also have to do the work of overcoming forward momentum to stop the forward motion of the bolt. Because the forward and rearward speeds of the bolt tend to be approximately the same, the API blowback allows the weight of the bolt to be halved.[7] Because the momentum of the two opposed bolt motions cancels out over time, the API blowback design results in reduced recoil.
The simplest form of API blowback is used in open bolt submachine guns.[8]In this configuration, the chamber depth is made a few thousandths of an inch shorter than the cartridge case's length. This causes the forward moving bolt's fixed firing pin to ignite the primer a moment before the bolt strikes the chamber face. While this simple version of the API design does not produce very important weight savings, it makes the firing cycle seem smoother to the operator and enhances controllability by reducing the submachine gun's muzzle climb. The heavy telescoping bolt's center of mass is forward of the submachine gun's center of gravity at the point of cartridge ignition. The telescoping bolt's inertial action pushes the submachine gun's muzzle forward and down, thereby reducing felt recoil and countering the recoiling cartridge's attempt to make the muzzle rise.
To make full use of the potential advantages of advanced primer ignition[7], larger calibre APIB guns such as the Becker and Oerlikon use extended chambers, longer than is necessary to contain the round, and straight-sided cases with rebated rims.[8] The last part of forward motion and the first part of the rearward motion of the case and bolt happen within the confines of this extended chamber. As long as the gas pressure in the barrel is high, the walls of case remain supported and the breach sealed, although the case is sliding rearwards. This sliding motion of the case, while it is expanded by a high internal gas pressure, risks tearing it apart, and a common solution is to grease the ammunition to reduce the friction. The case needs to have a rebated rim because the front end of the bolt will enter the chamber, and the extractor claw hooked over the rim therefore has to fit also within the diameter of the chamber. The case generally has very little neck, because this remains unsupported during the firing cycle and is generally deformed; a strongly necked case would be likely to split.
The API blowback design permits the use of more powerful ammunition in a lighter gun that would be achieved by using plain blowback, and the reduction of felt recoil results in further weight savings. The original Becker cannon, firing 20x70RB ammunition, was developed to be carried by WWI aircraft, and weighed only 30 kg.[9] Oerlikon even produced an anti-tank rifle firing 20x110RB ammunition using the API blowback mechanism, the SSG36. On the other hand, because the design imposes a very close relationship between bolt mass, chamber length, spring strength, ammunition power and rate of fire, in APIB guns high rate of fire and high muzzle velocity tend to be mutually exclusive.[8] API blowback guns also have to fire from an open bolt, which is not conducive to accuracy (although for short-ranged submachineguns this is less important) and means they can't be synchronized to fire through a propeller.
A schematic of the lever-delayed blowback mechanism used in the FAMAS assault rifle.
Lever-delayed blowback utilizes leverage to delay the opening of the breech[10]. When the cartridge pushes against the bolt face, the lever moves the bolt carrier rearward at an accelerated rate relative to the light bolt. This leverage significantly increases resistance and slows the movement of the lightweight bolt. John Pedersen patented the first known design for a lever-delay system.[11] The mechanism was adapted by Hungarian arms designer Pál Király (a.k.a. Paul de Kiraly) in the 1930s and first used in the Danuvia 43M submachine gun. Other weapons to use this system are the TKB-517/2B-A-40 assault rifles, the San Cristobal .30 carbine, the FAMAS[12], the BSM/9 M1 submachine gun, B76 pistol, AVB-7.62 rifle and the AA-52 machine gun.
A schematic of the roller-delayed blowback mechanism used in the MP5 submachine gun. This system had its origins in the late-war StG 45(M) assault rifle prototype.
Roller-delayed blowback was first used in the experimental MG 42 derivative MG 42V and the 1945 Mauser StG 45 prototypes. Roller-delayed blowback operation differs from roller-locked recoil operation as seen in the MG 42. Unlike the MG 42, in roller-delayed blowback the barrel is fixed and does not recoil. As the bolt head is driven rearward, rollers on the sides of the bolt are driven inward against a tapered bolt carrier extension. This forces the bolt carrier rearward at a much greater velocity and delays movement of the bolt head. The primary advantage of roller-delayed blowback is the simplicity of the design compared to gas or recoil operation.[13]
After WWII, former Mauser technicians Ludwig Vorgrimler and Theodor Löffler perfected this mechanism between 1946 and 1950 while working for the French Centre d'Etudes et d'Armament de Mulhouse (CEAM). The first full-scale production rifle to utilize roller-delay was the Spanish CETME followed by the Swiss Sturmgewehr 57, and the Heckler & Koch G3 rifle. The MP5 submachine gun is the most common weapon in service worldwide still using this system. The P9 pistol also uses roller-delayed blowback; however, the Czech vz. 52 is roller-locked.
Operation of the Schwarzlose machine gun.
In toggle-delayed blowback firearms, the rearward motion of the breechblock must overcome significant mechanical leverage.[16] The bolt is hinged in the middle, stationary at the rear end and nearly straight at rest. As the breech moves back under blowback power, the hinge joint moves upward. The leverage disadvantage keeps the breech from opening until the bullet has left the barrel and pressures have dropped to a safe level. This mechanism was used on the Pedersen rifle and Schwarzlose MG M.07/12 machine gun. [17] Modern high-pressure blowback systems such as the HK G3 incorporate fluted chambers to facilitate extraction. Lacking fluted chambers, previous toggle-locked firearms required cases lubricated with wax (Pedersen) or oil (Schwarzlose).
The difference between Blowback and Blow-forward.
A firearm operation where the barrel is virtually the only moving part of the weapon that is forced forward against a spring by the cartridge pressure and friction of the projectile against the rifling. Only a few weapons such as the Steyr Mannlicher M1894, Schwarzlose Model 1908, Hino Komuro M1908 Pistol, Mk 20 Mod 0 40mm automatic grenade launcher, the Special Operations Weapon and Pancor Jackhammer the last known weapons to use this operation.
Several types of blowback systems exist within this broad principle of operation, each distinguished by the level of energy derived through the blowback principle and the methods utilized in controlling bolt movement. In most actions utilizing blowback operation, the breech is not mechanically locked at the time of firing: the inertia of the bolt and recoil spring(s), relative to the weight of the bullet, delays opening of the breech until the bullet has left the barrel.[2] A few locked breech designs use a form of blowback (example: primer actuation) to perform the unlocking function.
Other operating principles for self-loading firearms include gas operation, recoil operation, Gatling, and chain. The blowback principle may be considered a simplified form of gas operation, since the cartridge case behaves like a piston driven by the powder gases.[1]
Principle of operation
The blowback system is generally defined as an operating system in which energy to operate the firearm's various mechanisms and provide automation is derived from the movement of the spent cartridge case pushed out of the chamber by rapidly expanding powder gases.[3] This rearward thrust, imparted against the bolt, is a direct reaction of the total reaction to the forward thrust applied to the bullet and the expansion of propellant gases.[3] Certain guns will use all of the energy from blowback to perform the entire operating cycle (these are typically designs using relatively "low power" ammunition) while others will use only a portion of the blowback to operate certain parts of the cycle or simply use the blowback energy to enhance the operational energy from another system of automatic operation.[3]What is common to all blowback systems is that the cartridge case must move under the direct action of the powder pressure, therefore any gun in which the bolt is not rigidly locked and permitted to move while there remains powder pressure in the chamber will undergo a degree of blowback action.[3] The energy from the burnt gases appears in the form of kinetic energy transmitted to the bolt mechanism, which is controlled and used to operate the firearm's operation cycle. The extent to which blowback is employed largely depends on the manner used to control the movement of the bolt and the proportion of energy drawn from other systems of operation.[1] It is with how the movement of the bolt is controlled where blowback systems differ. Blowback operation is most often divided into three categories, all using residual pressure to complete the cycle of operation: simple blowback, advanced primer ignition and delayed blowback or retarded blowback.
Simple blowback
The cycle begins when the cartridge is fired. Expanding gases from the fired round send the projectile down the barrel and at the same time force the case against the breech face of the bolt, overcoming the inertia of the bolt, resulting in a "blow back" effect. The forces exerted by the powder gases exist for only a relatively brief moment; lingering residual gases continue to act on the case for an even shorter period of time. The breech is kept sealed by the cartridge case until the bullet has left the barrel and gas pressure has dropped to a safe level; the inertia of the bolt mass ensures this.[4] At this point the powder pressure is zero and the force driving the bolt back is also zero, but the case and bolt continue to the rear of their own momentum.[4] As the bolt travels back, the spent cartridge case is extracted and then ejected, and the firing mechanism is cocked while the bolt begins to decelerate against the resistance provided by the recoil or action spring. The bolt eventually reaches a velocity of zero and the kinetic energy from the recoil impulse is now stored in the compressed spring (some energy loss does occur due to friction and the extraction and ejection sequences).[4] The action spring then propels the bolt forward again, which strips a round from the feed system along the way. The bolt carries a new cartridge into the chamber with considerable velocity and the action spring completes its energy transfer just prior to return to battery. The forward velocity is entirely dissipated upon impact with the chamber face.[4]
To remain practical, this system is only suitable for firearms using relatively low pressure cartridges. Pure blowback operation is typically found on semi-automatic, small-caliber pistols, small-bore semi-automatic rifles and submachine guns. Some low-velocity cannon and grenade launchers such as the Mk 19 grenade launcher also use blowback operation.
The barrel of a blowback pistol is generally fixed to the frame and the slide is held against the barrel only by the recoil spring tension. The slide starts to move rearward immediately upon ignition of the primer. As the cartridge moves rearward with the slide, it is extracted from the chamber and typically ejected clear of the firearm. The mass of the slide must be sufficient to hold the breech closed until the bullet exits the barrel and residual pressure is vented from the bore. A cartridge with too high a pressure or a slide with too little mass may cause the cartridge case to extract early, causing a separation or rupture. This generally limits blowback pistol designs to calibers less powerful than 9x19mm Parabellum (.25 ACP, .32 ACP, .380 ACP, 9x18mm Makarov etc.). Any larger and the slide mass starts to become excessive, and therefore few blowback handguns in such calibers exist; the most notable exceptions are simple, inexpensive guns such as those made by Hi-Point Firearms which includes models chambered in .45 ACP, .40 S&W, .380 ACP and 9x19mm Parabellum.[5]
Most simple blowback rifles are chambered for the .22 Long Rifle cartridge. Popular examples include the Marlin Model 60 and the Ruger 10/22. Some blowback rifles or carbines are chambered for pistol cartridges, such as the 9mm Parabellum, .40 S&W and .45 ACP. Examples include the Ruger Police Carbine, Beretta Cx4 Storm, Marlin Camp Carbine and Hi-Point Carbine. There were also a few rifles that chambered cartridges specifically designed for blowback operation. Examples include the Winchester Model 1905, 1907 and 1910. A very unusual blowback rifle was created by fitting the M1903 Springfield rifle with a mechanism called the Pedersen device.
API blowback
Advanced Primer Ignition (API) was originally developed by Reinhold Becker[6] for use on the Becker 20-mm automatic cannon. It became a feature of a wide range of automatic weapons, including the Oerlikon cannon widely used as anti-aircraft weapons during WWII. A simpler form of API blowback is very widely used on submachine guns.In the API blowback design, the cartridge has not been fully chambered and the bolt is still moving forward when the primer ignited. In a plain blowback design, the propellant gases have to overcome static inertia to accelerate the bolt rearwards to open the breech. In an API blowback, they also have to do the work of overcoming forward momentum to stop the forward motion of the bolt. Because the forward and rearward speeds of the bolt tend to be approximately the same, the API blowback allows the weight of the bolt to be halved.[7] Because the momentum of the two opposed bolt motions cancels out over time, the API blowback design results in reduced recoil.
The simplest form of API blowback is used in open bolt submachine guns.[8]In this configuration, the chamber depth is made a few thousandths of an inch shorter than the cartridge case's length. This causes the forward moving bolt's fixed firing pin to ignite the primer a moment before the bolt strikes the chamber face. While this simple version of the API design does not produce very important weight savings, it makes the firing cycle seem smoother to the operator and enhances controllability by reducing the submachine gun's muzzle climb. The heavy telescoping bolt's center of mass is forward of the submachine gun's center of gravity at the point of cartridge ignition. The telescoping bolt's inertial action pushes the submachine gun's muzzle forward and down, thereby reducing felt recoil and countering the recoiling cartridge's attempt to make the muzzle rise.
To make full use of the potential advantages of advanced primer ignition[7], larger calibre APIB guns such as the Becker and Oerlikon use extended chambers, longer than is necessary to contain the round, and straight-sided cases with rebated rims.[8] The last part of forward motion and the first part of the rearward motion of the case and bolt happen within the confines of this extended chamber. As long as the gas pressure in the barrel is high, the walls of case remain supported and the breach sealed, although the case is sliding rearwards. This sliding motion of the case, while it is expanded by a high internal gas pressure, risks tearing it apart, and a common solution is to grease the ammunition to reduce the friction. The case needs to have a rebated rim because the front end of the bolt will enter the chamber, and the extractor claw hooked over the rim therefore has to fit also within the diameter of the chamber. The case generally has very little neck, because this remains unsupported during the firing cycle and is generally deformed; a strongly necked case would be likely to split.
The API blowback design permits the use of more powerful ammunition in a lighter gun that would be achieved by using plain blowback, and the reduction of felt recoil results in further weight savings. The original Becker cannon, firing 20x70RB ammunition, was developed to be carried by WWI aircraft, and weighed only 30 kg.[9] Oerlikon even produced an anti-tank rifle firing 20x110RB ammunition using the API blowback mechanism, the SSG36. On the other hand, because the design imposes a very close relationship between bolt mass, chamber length, spring strength, ammunition power and rate of fire, in APIB guns high rate of fire and high muzzle velocity tend to be mutually exclusive.[8] API blowback guns also have to fire from an open bolt, which is not conducive to accuracy (although for short-ranged submachineguns this is less important) and means they can't be synchronized to fire through a propeller.
Delayed blowback
For more powerful rounds or for a lighter operating mechanism, some system of delayed or retarded blowback is often used, requiring the bolt to overcome some initial resistance while not fully locked. Because of high pressures, rifle-caliber delayed blowback firearms, such as the FAMAS, have fluted chambers to ease extraction. There are various delay mechanisms:Lever delayed
Roller delayed
After WWII, former Mauser technicians Ludwig Vorgrimler and Theodor Löffler perfected this mechanism between 1946 and 1950 while working for the French Centre d'Etudes et d'Armament de Mulhouse (CEAM). The first full-scale production rifle to utilize roller-delay was the Spanish CETME followed by the Swiss Sturmgewehr 57, and the Heckler & Koch G3 rifle. The MP5 submachine gun is the most common weapon in service worldwide still using this system. The P9 pistol also uses roller-delayed blowback; however, the Czech vz. 52 is roller-locked.
Gas delayed
Gas-delayed blowback should not be confused with gas-operated. The bolt is never locked, and so is pushed rearward by the expanding propellant gases as in other blowback-based designs. However, propellant gases are vented from the barrel into a cylinder with a piston that delays the opening of the bolt. It is used by Volkssturmgewehr 1-5 rifle, the Heckler & Koch P7, Steyr GB and M-77B pistols.Chamber-ring delayed
When a cartridge is fired, the case expands to seal the sides of the chamber. This seal prevents high-pressure gas from escaping into the action of the gun. Because a conventional chamber is slightly oversized, an unfired cartridge will enter freely. In a chamber-ring delayed firearm, the chamber is conventional in every respect except for a raised portion at the rear of smaller diameter than the front of the chamber. When the case expands in the front of the chamber and pushes rearward on the slide, it is slowed as this raised portion constricts the expanded portion of the case as the case is extracted. The Seecamp pistol operates on this principle.Off-axis bolt travel
John Browning developed this simple method whereby the axis of bolt movement was not in line with that of the bore.[14] The result was that a small rearward movement of the bolt in relation to the bore axis required a greater movement along the axis of bolt movement, essentially magnifying the resistance of the bolt without increasing its mass. The French MAS-38 submachine gun of 1938 utilizes a bolt whose path of recoil is at an angle to the barrel. The Jatimatic and TDI Vector use modified versions of this concept.Toggle delayed
Hesitation locked
John Pedersen's patented system uses a separate breech block within the slide or bolt carrier. When in battery, the breech block rests slightly forward of the locking shoulder in the frame. When the cartridge is fired, the bolt and slide move together a short distance rearward powered by the energy of the cartridge as in a standard blowback system. When the breech block contacts the locking shoulder, it stops, locking the breech in place. The slide continues rearward with the momentum it acquired in the initial phase. This allows chamber pressure to drop to safe levels while the breech is locked and the cartridge slightly extracted. Once the bullet leaves the barrel and pressure drops, the continuing motion of the slide lifts the breech block from its locking recess through a cam arrangement, continuing the firing cycle. The Remington 51 pistol was the only production firearm to utilize this type of operating system.Tilting bolt
The Reising submachine gun, Models 50 and 55, and semi-automatic carbine Model 60, used a bolt that tilted up into a recess in the receiver. Unlike the fully-locked tilting bolt of the Savage 99 rifle, the Reising bolt was not mechanically locked in position and the action functions as a friction delayed blowback.[18]Screw-delayed
First used on the Mannlicher retarded blowback rifle of 1893, the bolt in screw-delayed blowback was slowed by the need to rotate steeply pitched interrupted threads on the bolt and receiver. John T. Thompson designed a rifle that operated on a similar principle around 1920 and submitted it for trials with the US Army. This rifle, submitted multiple times, competed unsuccessfully against the Pedersen rifle and Garand primer-actuated rifle in early testing to replace the M1903 Springfield rifle.[19] Mikhail Kalashnikov later developed a prototype submachine gun in 1942 that operated by a screw-delayed blowback principle[20], which is also found on the Fox Wasp carbine. A pair of telescoping screws delayed rearward movement of the operating parts during the firing cycle. This weapon was ultimately not selected for production.[21] The screw-delayed action is similar to the Blish lock although Mannlicher's prototype pre-dates the Blish patent.Other blowback systems
Floating chamber
David Marshall Williams (a noted designer for the U.S. Ordnance Office and later Winchester) developed a mechanism to allow firearms designed for full-sized cartridges to fire .22 caliber rimfire ammunition reliably. His system used a small 'piston' that incorporates the chamber. When the cartridge is fired, the front of the piston is thrust back with the cartridge giving a significant push to the bolt. Often described as accelerated blowback, this amplifies the otherwise anemic recoil energy of the .22 rimfire cartridge.[22] Williams designed a training version of the Browning machine gun and the Colt Service Ace .22 long rifle version of the M1911 using his system. The floating chamber is both a blowback and gas operated mechanism.[23]Primer actuated
Primer actuated firearms utilize blowback force to set the primer back to operate a mechanism to unlock and cycle the firearm. John T. Kewish and John Garand were the first to develop the system in an unsuccessful bid to replace the M1903 bolt action rifle.[24] (The U.S. military adopted ammunition with crimped primers that do not set back. Another Garand design was eventually accepted.) AAI Corporation used their developmental piston primer mechanism in a rifle submitted for the SPIW competition.[25] A similar system is used in the spotting rifles on the LAW 80 and Shoulder-launched Multipurpose Assault Weapon use a 9mm, .308 Winchester based cartridge with a .22 Hornet blank cartridge in place of the primer. Upon firing, the Hornet case sets back a short distance, unlocking the action.[26]Limited-utility designs
Blow-Forward
Blish lock
Main article: Blish lock
The Blish Lock is a breech locking mechanism designed by John Bell Blish based upon his observation that under extreme pressures, certain dissimilar metals will resist movement with a force greater than normal friction laws would predict. In modern engineering terminology, it is called static friction, or stiction. His locking mechanism was used in the Thompson submachine gun, Autorifle and Autocarbine designs. This dubious principle was later eliminated as redundant in the .45 caliber submachine gun. Any actual advantage could also be attained by adding a mere ounce of mass to the bolt.Savage rotating barrel
The Savage system employed the theory that the rifling in the barrel caused a rotational force that would hold the gun locked until the projectile left the barrel. It was later discovered that the bullet had left the barrel long before any locking could occur. Savage pistols were in fact operating as pure blowback firearms. [27]Tuesday, February 12, 2013
Romanian Side-Folder AK Build
I am getting ready to build my first AK. Would have done it sooner, but I kept putting it off, and then kits kinda' dried up... Anyhoo, a few relatively cheap kits are available now, so I'm going for a budget build.
I ordered one of the $120 Romy M90 sidefolder kits from Centerfire, with no barrel. I found a Romy barrel somewhere else, a Tapco flat and rivet set at another place, and some magazines at yet another place. The only thing that has arrived so far is the kit, and it looks good. I will post pics soon.
I cleaned the kit in gasoline today to remove the cosmoline.
Hopefully the other parts will show up early next week, and I can get started in earnest.
Update: I got my barrel from ak-47s.com. It was $100 plus $13.something shipping. Not cheap, but it is the same price as the new US barrels. I was willing to pay that because it has a chrome-plated bore and chamber, which the US-made ones do not. It has a perfect, like-new bore, so I am happy with it. Hopefully it won't be too much trouble to get the headspace right.
I used a jig, ball pein hammer, and vise to bend the flat. A friend has the jig and let me borrow it. I plan to build my own jig using an ingenious design I saw that allows use of either a press or hammer and anvil; but I am glad I used the simple "beat it over a jig with a hammer" method to give my first AK build that certain Khyber Pass look.
Speaking of the Khyber Pass look, it is ugly after I heat-treated it. I couldn't quickly find my welding goggles, so I took that as a good excuse to pay a visit to the Harbor Freight store and pick up a new one. The goggles seemed awfully dark, and I discovered later that they had #10 filters in them, which are intended for arc welding and are too dark for use with a gas torch. Bottom line, I heated the holes 'til I could see the glow, at which point they were too hot and starting to become malformed. I'm gonna use this receiver anyway; I am naming it "Mal" for all the ugly points and in honor of Mal Reynolds, who always had ugly guns.
I ordered one of the $120 Romy M90 sidefolder kits from Centerfire, with no barrel. I found a Romy barrel somewhere else, a Tapco flat and rivet set at another place, and some magazines at yet another place. The only thing that has arrived so far is the kit, and it looks good. I will post pics soon.
I cleaned the kit in gasoline today to remove the cosmoline.
Hopefully the other parts will show up early next week, and I can get started in earnest.
Update: I got my barrel from ak-47s.com. It was $100 plus $13.something shipping. Not cheap, but it is the same price as the new US barrels. I was willing to pay that because it has a chrome-plated bore and chamber, which the US-made ones do not. It has a perfect, like-new bore, so I am happy with it. Hopefully it won't be too much trouble to get the headspace right.
I used a jig, ball pein hammer, and vise to bend the flat. A friend has the jig and let me borrow it. I plan to build my own jig using an ingenious design I saw that allows use of either a press or hammer and anvil; but I am glad I used the simple "beat it over a jig with a hammer" method to give my first AK build that certain Khyber Pass look.
Speaking of the Khyber Pass look, it is ugly after I heat-treated it. I couldn't quickly find my welding goggles, so I took that as a good excuse to pay a visit to the Harbor Freight store and pick up a new one. The goggles seemed awfully dark, and I discovered later that they had #10 filters in them, which are intended for arc welding and are too dark for use with a gas torch. Bottom line, I heated the holes 'til I could see the glow, at which point they were too hot and starting to become malformed. I'm gonna use this receiver anyway; I am naming it "Mal" for all the ugly points and in honor of Mal Reynolds, who always had ugly guns.
Monday, February 11, 2013
Building The Mujahadeen AR-15
How to finish an 80% AR lower receiver using hand tools. Says the author;
"I'm not a machinist, tool maker or mechanic. I was a tank mechanic in the Army, but most Army mechanics are only parts changers. I was a good parts changer. I am now a human resources manager for a computer hardware manufacturer. I am also a patriot and a pretty good jury rigger. (Someday I'll with a book called "Doing the Job Right With the Wrong Tool!") Before I started this project, I set limits on the tools, power, equipment, supplies and outside help. I have less than the average amount of tools; a 3/8" drill, a set of bits up to 1/2", a set of files, sandpaper, a hacksaw, a Handy Clamp clamp (my vise), a package of JB Weld (good stuff), a DPMS lower, a Model 1 parts kit, a pack of Red Man and a box of Band-Aids."
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Ed's Red Homebrew Gun Cleaning Solvent
''Ed's Red'' Bore Cleaner... Home-Mix Really Works
By C.E. ''Ed'' Harris
Updated & Revised 9-29-95.
Four years ago I mixed my first "Ed's Red" or "ER" bore cleaner and
hundreds of users have told me that they think this home-mixed cleaner
is more effective than commercial products. I urge you to mix some and
give it a fair trial, compared to whatever you have been using.
Competitive shooters, gun clubs and police departments who use a gallon
or more of rifle bore cleaner annually can save by mixing their own, and
they will give up nothing in safety or effectiveness.
This cleaner has an action very similar to standard military issue rifle
bore cleaner, such as Mil-C-372B. Users report it is more effective than
Hoppe's for removing plastic fouling in shotgun bores, or caked carbon
fouling in semi-automatic rifles or pistols, or in removing leading in
revolvers. It is not as effective as Sweets 7.62, Hoppe's Bench Rest
Nine or Shooter's Choice for fast removal of heavy copper fouling in
rifle bores. However, because "ER" is more effective in removing caked
carbon and abrasive primer residues than other cleaners, metal fouling
is greatly reduced when "ER" is used on a continuing basis.
I originally came up with this mix because I am an active high power
rifle competitive shooter and hand loading experimenter who uses a lot
of rifle bore cleaner. I was not satisfied with the performance and high
price of commercial products. I knew there was no technical reason why
an effective firearm bore cleaner couldn't be mixed using common
hardware store ingredients. The result is inexpensive, effective,
provides good corrosion protection and adequate residual lubrication so
that routine "oiling" after cleaning is rarely necessary, except for
long-term storage of over 1 year, or harsh service environments, such as
salt water exposure.
This formula is based on proven principles and incorporates two polar
and two nonpolar solvents. It is adapted from the one in Hatcher's
Notebook for "Frankford Arsenal Cleaner No.18," but substituting
equivalent modern materials. I had the help of an organic chemist in
doing this and we knew there would be no "surprises." The original
Hatcher formula called for equal parts of acetone, turpentine, Pratts
Astral Oil and sperm oil, and optionally 200 grams of anhydrous lanolin
added per liter. Some discussion of the ingredients is helpful to
understand the properties of the cleaner and how it works.
Pratts Astral oil was nothing more than acid free, deodorized kerosene.
I recommend "K1" kerosene of the type normally sold for use in indoor
space heaters. Some users have reported successful substitution of
civilian aviation grade kerosene such as Turbo-A. I am reluctant to
"recommend" substitution of aviation grade kerosene, because the effects
upon firearm components of the additives required in aviation fuels are
unknown. Some "jet- fuels" are gasoline/kerosene blends and absolutely
should not be used, because of their increased flammability.
An inexpensive, effective substitute for sperm oil is Dexron (II, IIe or
III) automatic transmission fluid. Prior to about 1950 that most ATF's
were sperm oil based, but during WWII a synthetic was developed for use
in precision instruments. With the great demand for automatic
transmission autos after WWII, sperm oil was no longer practical to
produce ATF in the quantity demanded, so the synthetic material became
the basis for the Dexron fluids we know today. The additives in ATFs
which include organometallic antioxidants and surfactants, make it
highly suitable for inclusion in an all-purpose
cleaner-lubricant-preservative.
Hatcher's original Frankford Arsenal No. 18 formula used gum spirits of
turpentine. Because turpentine is expensive today, and is also an
"aromatic" solvent, which is highly flammable, I chose not to use it.
Safer and cheaper is "aliphatic mineral spirits," a petroleum based
"safety solvent" used for thinning oil based paints and also widely used
as an automotive parts cleaner. It is commonly sold under the names
"odorless mineral spirits," "Stoddard Solvent" or "Varsol".
Acetone is included in "ER" to provide an aggressive, fast-acting
solvent for caked powder residues. Because acetone is an aromatic,
organic solvent, it is recommended that users leave it out if the
cleaner will be used in enclosed spaces lacking forced air ventilation.
The acetone in ER will evaporate, liberating volatile organic compounds
(VOCs) into the atmosphere unless containers are kept tightly closed
when not in use. The cleaner is still effective without the acetone, but
it is not as "fast-acting."
There isn't anything in Ed's Red which chemically dissolves copper
fouling in rifle bores, but it does a better job removing on carbon and
primer residue than anything else which is safe and commonly available.
Numerous users have told me, that exclusive use of "ER" reduces copper
deposits, because it removes the old impacted powder fouling which is
left by other cleaners, which reduces the abrasion and adhesion of
jacket metal to the bore surface, leaving a cleaner surface condition
which reduces subsequent fouling. Experience seems to indicate that "ER"
will actually remove metal fouling it if you let it "soak," so the
surfactants will do the job, though you have to be patient.
Addition of the lanolin to ER bore cleaner mix is entirely optional. The
cleaner works quite well and gives adequate corrosion protection and
lubrication for most users without it. Incorporating the lanolin makes
the cleaner easier on the hands, and increases lubricity and film
strength, and improves corrosion protection if weapons will be routinely
exposed to salt air, water spray, industrial or urban corrosive
atmospheres, or if you intend to use the cleaner as a protectant for
long term storage of over 1 year.
If you use other protective films for adverse use or long term storage
you can leave the lanolin out and save about $8 per gallon. At current
retail prices you can buy all the ingredients to mix ER, without the
lanolin for about $10 per gallon. I urge you to mix some yourself. I am
confident it will work as well for you as it does for me and hundreds of
users who got the "recipe" on the Fidonet Firearms Echo.
CONTENTS: Ed's Red Bore Cleaner
1 part Dexron II, IIe or III ATF, GM Spec. D-20265 or later.
1 part Kerosene - deodorized, K1
1 part Aliphatic Mineral Spirits, Fed. Spec. TT-T-2981F, CAS
#64741-49-9, or may substitute "Stoddard Solvent", CAS #8052-41-3, or
equivalent, (aka "Varsol")
1 part Acetone, CAS #67-64-1.
(Optional up to 1 lb. of Lanolin, Anhydrous, USP per gallon, OK to
substitute Lanolin, Modified, Topical Lubricant, from the drug store)
MIXING INSTRUCTIONS FOR "ER" BORE CLEANER:
Mix outdoors, in good ventilation. Use a clean 1 gallon metal,
chemical-resistant, heavy gage PET or PVC plastic container. NFPA
approved plastic gasoline storage containers are also OK. Do NOT use
HDPE, which is permeable, because the acetone will eventually evaporate.
The acetone in ER will also attack HDPE, causing the container to
collapse, making a heck of a mess!
Add the ATF first. Use the empty container to measure the other
components, so that it is thoroughly rinsed. If you incorporate the
lanolin into the mixture, melt this carefully in a double boiler, taking
precautions against fire. Pour the melted lanolin it into a larger
container, rinsing the lanolin container with the bore cleaner mix, and
stirring until it is all dissolved.
I recommend diverting a small quantity, up to 4 ozs. per quart of the
50-50 ATF/kerosene mix for optional use as an "ER-compatible" gun oil.
This can be done without impairing the effectiveness of the remaining
mix.
LABEL AND NECESSARY SAFETY WARNINGS:
RIFLE BORE CLEANER CAUTION: FLAMMABLE MIXTURE
HARMFUL IF SWALLOWED. KEEP OUT OF REACH OF CHILDREN
1. Flammable mixture. Keep away from heat, sparks or flame.
2. FIRST AID, If swallowed DO NOT induce vomiting, call physician
immediately. In case of eye contact immediately flush thoroughly with
water and call a physician. For skin contact wash thoroughly.
3. Use with adequate ventilation. Avoid breathing vapors or spray mist.
It is a violation of Federal law to use this product in a manner
inconsistent with its labelling. Reports have associated repeated and
prolonged occupational overexposure to solvents with permanent brain and
nervous system damage. If using in closed armory vaults lacking forced
air ventilation wear respiratory protection meeting NIOSH TC23C or
equivalent. Keep container tightly closed when not in use.
INSTRUCTIONS FOR USING "Ed's Red (ER)" Bore Cleaner:
1. Open the firearm action and ensure the bore is clear. Cleaning is
most effective when done while the barrel is still warm to the touch
from firing. Saturate a cotton patch with bore cleaner, wrap or impale
on jag and push it through the bore from breech to muzzle. The patch
should be a snug fit. Let the first patch fall off and do not pull it
back into the bore.
2. Wet a second patch, and similarly start it into the bore from the
breech, this time scrubbing from the throat area forward in 4-5" strokes
and gradually advancing until the patch emerges out the muzzle. Waiting
approximately 1 minute to let the bore cleaner soak will improve its
action.
3. For pitted, heavily carbon-fouled "rattle battle" guns, leaded
revolvers or neglected bores a bronze brush wet with bore cleaner may be
used to remove stubborn deposits. This is unnecessary for smooth,
target-grade barrels in routine use.
4. Use a final wet patch pushed straight through the bore to flush out
loosened residue dissolved by Ed's Red. Let the patch fall off the jag
without pulling it back into the bore. If you are finished firing,
leaving the bore wet will protect it from rust for 1 year under average
conditions.
5. If the lanolin is incorporated into the mixture, it will protect the
firearm from rust for up to two years. For longer term storage I
recommend use of Lee Liquid Alox as a Cosmolene substitute. "ER" will
readily remove hardened Alox or Cosmolene.
6. Wipe spilled Ed's Red from exterior surfaces before storing the gun.
While Ed's Red is harmless to blue and nickel finishes, the acetone it
contains is harmful to most wood finishes).
7. Before firing again, push two dry patches through the bore and dry
the chamber, using a patch wrapped around a suitably sized brush or jag.
First shot point of impact usually will not be disturbed by Ed's Red if
the bore is cleaned as described.
8. I have determined to my satisfaction that when Ed's Red is used
exclusively and thoroughly, that hot water cleaning is unnecessary after
use of Pyrodex or military chlorate primers. However, if bores are not
wiped between shots and shots and are heavily caked from black powder
fouling, hot water cleaning is recommended first to break up heavy
fouling deposits. Water cleaning should be followed by a thorough flush
with Ed's Red to prevent after-rusting which could result from residual
moisture. It is ALWAYS good practice to clean TWICE, TWO DAYS APART
whenever using chlorate primed ammunition, just to make sure you get all
the corrosive residue out.
This "Recipe" is placed in the public domain, and may be freely
distributed provided that it is done so in its entirely with all current
revisions, instructions and safety warnings included herein, and that
proper attribution is given to the author.
In Home Mix We Trust, Regards, Ed
By C.E. ''Ed'' Harris
Updated & Revised 9-29-95.
Four years ago I mixed my first "Ed's Red" or "ER" bore cleaner and
hundreds of users have told me that they think this home-mixed cleaner
is more effective than commercial products. I urge you to mix some and
give it a fair trial, compared to whatever you have been using.
Competitive shooters, gun clubs and police departments who use a gallon
or more of rifle bore cleaner annually can save by mixing their own, and
they will give up nothing in safety or effectiveness.
This cleaner has an action very similar to standard military issue rifle
bore cleaner, such as Mil-C-372B. Users report it is more effective than
Hoppe's for removing plastic fouling in shotgun bores, or caked carbon
fouling in semi-automatic rifles or pistols, or in removing leading in
revolvers. It is not as effective as Sweets 7.62, Hoppe's Bench Rest
Nine or Shooter's Choice for fast removal of heavy copper fouling in
rifle bores. However, because "ER" is more effective in removing caked
carbon and abrasive primer residues than other cleaners, metal fouling
is greatly reduced when "ER" is used on a continuing basis.
I originally came up with this mix because I am an active high power
rifle competitive shooter and hand loading experimenter who uses a lot
of rifle bore cleaner. I was not satisfied with the performance and high
price of commercial products. I knew there was no technical reason why
an effective firearm bore cleaner couldn't be mixed using common
hardware store ingredients. The result is inexpensive, effective,
provides good corrosion protection and adequate residual lubrication so
that routine "oiling" after cleaning is rarely necessary, except for
long-term storage of over 1 year, or harsh service environments, such as
salt water exposure.
This formula is based on proven principles and incorporates two polar
and two nonpolar solvents. It is adapted from the one in Hatcher's
Notebook for "Frankford Arsenal Cleaner No.18," but substituting
equivalent modern materials. I had the help of an organic chemist in
doing this and we knew there would be no "surprises." The original
Hatcher formula called for equal parts of acetone, turpentine, Pratts
Astral Oil and sperm oil, and optionally 200 grams of anhydrous lanolin
added per liter. Some discussion of the ingredients is helpful to
understand the properties of the cleaner and how it works.
Pratts Astral oil was nothing more than acid free, deodorized kerosene.
I recommend "K1" kerosene of the type normally sold for use in indoor
space heaters. Some users have reported successful substitution of
civilian aviation grade kerosene such as Turbo-A. I am reluctant to
"recommend" substitution of aviation grade kerosene, because the effects
upon firearm components of the additives required in aviation fuels are
unknown. Some "jet- fuels" are gasoline/kerosene blends and absolutely
should not be used, because of their increased flammability.
An inexpensive, effective substitute for sperm oil is Dexron (II, IIe or
III) automatic transmission fluid. Prior to about 1950 that most ATF's
were sperm oil based, but during WWII a synthetic was developed for use
in precision instruments. With the great demand for automatic
transmission autos after WWII, sperm oil was no longer practical to
produce ATF in the quantity demanded, so the synthetic material became
the basis for the Dexron fluids we know today. The additives in ATFs
which include organometallic antioxidants and surfactants, make it
highly suitable for inclusion in an all-purpose
cleaner-lubricant-preservative.
Hatcher's original Frankford Arsenal No. 18 formula used gum spirits of
turpentine. Because turpentine is expensive today, and is also an
"aromatic" solvent, which is highly flammable, I chose not to use it.
Safer and cheaper is "aliphatic mineral spirits," a petroleum based
"safety solvent" used for thinning oil based paints and also widely used
as an automotive parts cleaner. It is commonly sold under the names
"odorless mineral spirits," "Stoddard Solvent" or "Varsol".
Acetone is included in "ER" to provide an aggressive, fast-acting
solvent for caked powder residues. Because acetone is an aromatic,
organic solvent, it is recommended that users leave it out if the
cleaner will be used in enclosed spaces lacking forced air ventilation.
The acetone in ER will evaporate, liberating volatile organic compounds
(VOCs) into the atmosphere unless containers are kept tightly closed
when not in use. The cleaner is still effective without the acetone, but
it is not as "fast-acting."
There isn't anything in Ed's Red which chemically dissolves copper
fouling in rifle bores, but it does a better job removing on carbon and
primer residue than anything else which is safe and commonly available.
Numerous users have told me, that exclusive use of "ER" reduces copper
deposits, because it removes the old impacted powder fouling which is
left by other cleaners, which reduces the abrasion and adhesion of
jacket metal to the bore surface, leaving a cleaner surface condition
which reduces subsequent fouling. Experience seems to indicate that "ER"
will actually remove metal fouling it if you let it "soak," so the
surfactants will do the job, though you have to be patient.
Addition of the lanolin to ER bore cleaner mix is entirely optional. The
cleaner works quite well and gives adequate corrosion protection and
lubrication for most users without it. Incorporating the lanolin makes
the cleaner easier on the hands, and increases lubricity and film
strength, and improves corrosion protection if weapons will be routinely
exposed to salt air, water spray, industrial or urban corrosive
atmospheres, or if you intend to use the cleaner as a protectant for
long term storage of over 1 year.
If you use other protective films for adverse use or long term storage
you can leave the lanolin out and save about $8 per gallon. At current
retail prices you can buy all the ingredients to mix ER, without the
lanolin for about $10 per gallon. I urge you to mix some yourself. I am
confident it will work as well for you as it does for me and hundreds of
users who got the "recipe" on the Fidonet Firearms Echo.
CONTENTS: Ed's Red Bore Cleaner
1 part Dexron II, IIe or III ATF, GM Spec. D-20265 or later.
1 part Kerosene - deodorized, K1
1 part Aliphatic Mineral Spirits, Fed. Spec. TT-T-2981F, CAS
#64741-49-9, or may substitute "Stoddard Solvent", CAS #8052-41-3, or
equivalent, (aka "Varsol")
1 part Acetone, CAS #67-64-1.
(Optional up to 1 lb. of Lanolin, Anhydrous, USP per gallon, OK to
substitute Lanolin, Modified, Topical Lubricant, from the drug store)
MIXING INSTRUCTIONS FOR "ER" BORE CLEANER:
Mix outdoors, in good ventilation. Use a clean 1 gallon metal,
chemical-resistant, heavy gage PET or PVC plastic container. NFPA
approved plastic gasoline storage containers are also OK. Do NOT use
HDPE, which is permeable, because the acetone will eventually evaporate.
The acetone in ER will also attack HDPE, causing the container to
collapse, making a heck of a mess!
Add the ATF first. Use the empty container to measure the other
components, so that it is thoroughly rinsed. If you incorporate the
lanolin into the mixture, melt this carefully in a double boiler, taking
precautions against fire. Pour the melted lanolin it into a larger
container, rinsing the lanolin container with the bore cleaner mix, and
stirring until it is all dissolved.
I recommend diverting a small quantity, up to 4 ozs. per quart of the
50-50 ATF/kerosene mix for optional use as an "ER-compatible" gun oil.
This can be done without impairing the effectiveness of the remaining
mix.
LABEL AND NECESSARY SAFETY WARNINGS:
RIFLE BORE CLEANER CAUTION: FLAMMABLE MIXTURE
HARMFUL IF SWALLOWED. KEEP OUT OF REACH OF CHILDREN
1. Flammable mixture. Keep away from heat, sparks or flame.
2. FIRST AID, If swallowed DO NOT induce vomiting, call physician
immediately. In case of eye contact immediately flush thoroughly with
water and call a physician. For skin contact wash thoroughly.
3. Use with adequate ventilation. Avoid breathing vapors or spray mist.
It is a violation of Federal law to use this product in a manner
inconsistent with its labelling. Reports have associated repeated and
prolonged occupational overexposure to solvents with permanent brain and
nervous system damage. If using in closed armory vaults lacking forced
air ventilation wear respiratory protection meeting NIOSH TC23C or
equivalent. Keep container tightly closed when not in use.
INSTRUCTIONS FOR USING "Ed's Red (ER)" Bore Cleaner:
1. Open the firearm action and ensure the bore is clear. Cleaning is
most effective when done while the barrel is still warm to the touch
from firing. Saturate a cotton patch with bore cleaner, wrap or impale
on jag and push it through the bore from breech to muzzle. The patch
should be a snug fit. Let the first patch fall off and do not pull it
back into the bore.
2. Wet a second patch, and similarly start it into the bore from the
breech, this time scrubbing from the throat area forward in 4-5" strokes
and gradually advancing until the patch emerges out the muzzle. Waiting
approximately 1 minute to let the bore cleaner soak will improve its
action.
3. For pitted, heavily carbon-fouled "rattle battle" guns, leaded
revolvers or neglected bores a bronze brush wet with bore cleaner may be
used to remove stubborn deposits. This is unnecessary for smooth,
target-grade barrels in routine use.
4. Use a final wet patch pushed straight through the bore to flush out
loosened residue dissolved by Ed's Red. Let the patch fall off the jag
without pulling it back into the bore. If you are finished firing,
leaving the bore wet will protect it from rust for 1 year under average
conditions.
5. If the lanolin is incorporated into the mixture, it will protect the
firearm from rust for up to two years. For longer term storage I
recommend use of Lee Liquid Alox as a Cosmolene substitute. "ER" will
readily remove hardened Alox or Cosmolene.
6. Wipe spilled Ed's Red from exterior surfaces before storing the gun.
While Ed's Red is harmless to blue and nickel finishes, the acetone it
contains is harmful to most wood finishes).
7. Before firing again, push two dry patches through the bore and dry
the chamber, using a patch wrapped around a suitably sized brush or jag.
First shot point of impact usually will not be disturbed by Ed's Red if
the bore is cleaned as described.
8. I have determined to my satisfaction that when Ed's Red is used
exclusively and thoroughly, that hot water cleaning is unnecessary after
use of Pyrodex or military chlorate primers. However, if bores are not
wiped between shots and shots and are heavily caked from black powder
fouling, hot water cleaning is recommended first to break up heavy
fouling deposits. Water cleaning should be followed by a thorough flush
with Ed's Red to prevent after-rusting which could result from residual
moisture. It is ALWAYS good practice to clean TWICE, TWO DAYS APART
whenever using chlorate primed ammunition, just to make sure you get all
the corrosive residue out.
This "Recipe" is placed in the public domain, and may be freely
distributed provided that it is done so in its entirely with all current
revisions, instructions and safety warnings included herein, and that
proper attribution is given to the author.
In Home Mix We Trust, Regards, Ed
Cheap, Quick Revolver Check
- Small flashlight. One of the tiny LED lights powered by a coin cell will suffice, as will any cheap, disposable penlight or any other pocket-size flashlight.
- Blade-type feeler gauge. You can get these at any auto-parts store for around five bucks or less. Make sure it has, at minimum, a 0.008" (eight thousandths) blade. In fact, you could get by with just that one blade if you want to minimize weight and bulk.
- A bullet of the correct size for the revolver in question. Note I said a bullet, not a cartridge. Sorry to be so blunt, but if you don't know the difference, learn more about guns before you buy one. If you are looking at a revolver at your local gunshop and you pull out a loaded round, the proprietor is very likely to draw his own, loaded gun. I would. Besides which, a loaded round won't work very well for this test. The bullet can be jacketed and of nominal groove diameter of the revolver in question (.357 for .38 Special and .357 Magnum, for example) or cast lead and a thousandth over nominal (.358 for .38 or .357).
- Two hex or Allen keys, in the sizes of 1/16-inch and 5/64-inch.
- Swing out the cylinder (or open the loading gate, in the case of a single action revolver) and check that all chambers are unloaded. Wipe the metal parts of the revolver with your cleaning rag, paying special attention to the front and rear faces of the cylinder, the breech area, and underneath the extractor star. Close the cylinder.
- Grasp the cylinder and move it fore and aft. There should be little to no discernible movement.
- Point the muzzle skyward and grasp the handle in your palm, with your thumb near the trigger. Cock the hammer. Pull and hold the trigger fully to the rear with your thumb, while controlling and lowering the hammer with your other hand. While continuing to hold the trigger to the rear, shine the flashlight into the muzzle and make sure the chamber aligns with the bore. If it doesn't, you will see a crescent of the cylinder face on one side or the other. If you see that, the revolver has timing issues and should be passed over. While continuing to hold the trigger back, rock (rotate) the cylinder from side to side. There will usually be some movement, but it should be minimal. Now release the trigger, cock and lower the hammer to bring up the next chamber, and repeat the process for each chamber.
- With the cylinder closed, point the muzzle at the floor. Cock and lower the hammer and hold the trigger to the rear. Insert the 0.008" blade of your feeler gauge through the gap between the cylinder face and the forcing cone (rear of the barrel). If it fits easily and with no drag, walk away. This revolver needs major work. If it fits but drags, it is at the outer limit of acceptability. I would still probably pass on that one, especially if the dealer has more revolvers like it. Ideally you want a 0.003" blade to fit, but a 0.006" blade to not fit; but a 0.006" fit with drag is still quite acceptable. The larger this gap, the lower the velocity with a given load; but it needs at least 0.003" clearance to prevent binding from firing residue and heat expansion. Repeat this test with all chambers.
- If you noticed significant fore-aft movement (end shake) in Step 2, you can check it like this: with the hammer down and your finger off the trigger, measure the barrel-to-cylinder gap (as in Step 4) of one chamber while pulling the cylinder to the rear. Then remove that blade and measure the gap while pushing the cylinder fully forward. Subtract the first measurement from the second; it should not exceed 0.004" (four thousandths).
- Open the cylinder, or remove it if the gun is a single-action. Insert the bullet lightly into the forcing cone. It should enter partially but not fully. If you can easily insert the bullet until its base is flush with the rear of the barrel, the forcing cone (and hence the barrel) is worn out. Now insert the bullet into each chamber throat in turn. A jacketed bullet should just slip into the chamber throats with no effort, but it should not be loose. A lead bullet should be a tight fit.
- Lastly, the headspace. Most people don't even check it on a revolver, but overly generous clearance here can cause misfires, reduce velocity and accuracy, and if you reload, cause your cases to wear out prematurely. The rough test is to just use the 5/64-inch Allen key. That is 0.07825" across the flats, and if you can insert that between the rear of the (unloaded) cylinder and the breech plate while holding the cylinder forward, the headspace is well beyond acceptable limits and needs a complete rebuild at best. For most common revolver cartridges, minimum headspace is 0.060". Maximum is 0.070" for magnums and 0.074" for non-magnums. That holds true for .38 Special, .357 Magnum, .44 Special/Magnum, and .45 Colt. If you are checking anything other than those, I suggest you look it up on the SAAMI website. Ok, assuming the 5/64 didn't fit (if it did, forget that revolver), try the 1/16-inch key. That is 0.0625" across the flats and about 0.069" across the points. If it will almost but not quite fit, it may still be right at the minimum headspace. That is actually a good thing. Your feeler gauge may have the right combination of blades to allow you to determine within a thousandth or so what the headspace is. If the 1/16-inch key fit, try gently turning it. As long as you can feel contact on both sides (cylinder and breech) as you turn it, it is within spec. Note that this doesn't apply to any revolver whose chambers are recessed to accept the case rim, like early Smith and Wesson Magnums. On those guns you will have to use a feeler gauge. 0.020" would be maximum, 0.010" preferable, and no minimum so long as the cylinder will close and rotate.
AR-15 Pistol Rifling Twist
I recently built this AR-15 pistol from a virgin lower receiver that had never been assembled into a rifle. In reading the gun forums concerning AR pistols, one of the recurring themes is that only a fast 1:7" rifling twist should be used in the shortest common AR pistol barrel length of 7.5 inches, because that barely allows over one full rifling turn.
By that thinking, it should be impossible for the typical .38 Special revolver to shoot accurately. One turn in 18 inches is a common twist rate for .38 Special and .357 Magnum, and even a 6 inch barrel only provides one third of a turn to the projectile.
I bought my AR-15 pistol barrel with a 1:9 inch twist. So far, it seems to shoot just fine.
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