Caliber conversion device
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A caliber conversion device is a device which can be used to non-permanently alter a firearm to allow it to fire a different cartridge than the one it was originally designed to fire. The different cartridge must be smaller in some dimensions than the original design cartridge, and since smaller cartridges are usually cheaper, the device allows less expensive fire practice.
Alternative names sometimes imply the type of dimensional difference. A chamber insert may be used for a shorter cartridge of similar base diameter. A supplemental chamber or cartridge adapter is typically used for a shorter cartridge of reduced diameter.[1] A cartridge conversion sleeve may include a short barrel of reduced bore diameter. Shotgun conversion sleeves may be called subgauge inserts, subgauge tubes, or gauge reducers.
Sleeves intended for
Altering cartridge length
The simplest conversion is one that alters the length of the cartridge used, allowing a shorter but otherwise similarly dimensioned cartridge to be fired. Commonly called chamber inserts, these conversions resemble the front of the case, and are inserted into the firearm by placing over the new cartridge and inserting both into the chamber of the firearm. This seats the chamber insert into the front of the chamber, where it remains after firing. Once inserted, the chamber insert will remain in place until removed with the use of a stuck case remover. The most commonly encountered chamber inserts are ones designed to convert .30-06 Springfield to the shorter 7.62×51mm NATO. Since the chamber insert remains in the chamber, this type of conversion will function in semi-automatic firearms, and is commonly used in military surplus arms such as the M1 Garand, allowing the use of often less expensive surplus military ammunition.[2]
Altering the cartridge diameter
The next level in complexity involves altering the diameter of the cartridge used, typically allowing a short, straight walled handgun cartridge to be used in a rifle. These are often called supplemental chambers or cartridge adapters, and the entire supplemental chamber is treated like a cartridge, being loaded and ejected as a unit with the smaller cartridge. Since the barrel of the firearm is used, the caliber of the cartridges must match. The most commonly encountered supplemental chambers are for .30 caliber rifles designed for .308-inch (7.8 mm) diameter bullets, to use .32 caliber handgun cartridges with bullet diameters of approximately .312-inch (7.9 mm). Cartridge adapters have also been made to use .38 caliber handgun cartridges with bullet diameters of approximately .357-inch (9.1 mm) in .35 caliber rifles designed for bullets of .358-inch (9.1 mm) diameter.[3]
Supplemental chambers in .22 caliber, and potentially .17 caliber as well, pose a special problem not shared by larger calibers. Rimfire cartridges, with their low cost, noise, and recoil, are ideal for use in a supplemental chamber, except for the fact that the firearm in question is almost certainly a centerfire design. This means that supplemental chambers that use a rimfire cartridge must also provide a special offset firing pin. This is a metal insert that fits behind the rimfire cartridge, and has an appropriate projection to act as a firing pin. When this insert is hit by the firearm's firing pin, it is pushed forwards, which causes it to crush the rim of the rimfire cartridge, igniting it. Use of the centerfire to rimfire conversion requires a longer case, and so is not suitable for short cartridges such as
Since the supplemental chambers are approximately the size of a normal loaded cartridge, they will usually feed from a magazine, though they will not provide sufficient energy to cycle an automatic action.[citation needed]
Altering the caliber
The most complete transformation is offered by the caliber conversion sleeve. These include not only a new chamber, but a new barrel as well, allowing a smaller diameter bullet to be fired. These sleeves may be significantly longer than a loaded cartridge, if the length of the parent cartridge is not sufficient to provide the desired performance. Unlike the other types of cartridge conversions, this type incorporates rifling to stabilize the bullet; the other types rely on the rifling in the firearm's barrel.[citation needed]
Chamber length sleeves
Chamber length sleeves are restricted in its overall length, where a short cartridge is used with a long parent cartridge. The sleeve is rifled up to the end of the sleeve. Since most cartridge cases are only about 5 cm (2.0 in) long, this provides a limited power advantage. On the other hand, these will function from magazines in the same way as supplemental chambers, and allow the use of inexpensive rimfire ammunition in firearms chambered in .22 caliber (5.56 mm) or smaller.[citation needed]
Greater than chamber length sleeves
Sleeves that exceed the chamber length are generally used in
The calibers supported by caliber conversion sleeves are limited by the difference between the calibers. The sleeve's barrel must be thick enough to provide structural integrity to the barrel, and so requires a large enough internal barrel diameter to hold the new barrel. One manufacturer has a .40 caliber (10 mm) minimum diameter for these inserts[5] in .22 rimfire caliber.
Some manufacturers offer caliber conversion sleeves for shotguns, which convert a shotgun into a rifle with the use of a rifled barrel.[6]
Shotguns
Inserts for shotguns are called subgauge inserts, and function in much the same manner as inserts for handguns or rifles. However, due to the nature of shotguns, the implications of using an insert differ.[citation needed]
Since
Rifled inserts are also available, to allow the use of handgun cartridges or relatively low-power rifle cartridges such as the 12 gauge
Automatic firearm conversions
Conversions for
These conversions typically convert the firearm from
One exception to the use of a special lightweight bolt was the
Another cartridge conversion was the
Uses
In addition to often being less expensive than the larger cartridge, the smaller cartridges offer much reduced recoil and muzzle blast. Potential utility for short range target practice or killing small pests is limited by significantly reduced accuracy of handgun bullets encountering faster rifling twist after gaining velocity in the long jump through the unrifled adapter.[13] Low-powered ammunition, such as the .22 LR, allows the use of indoor ranges or outdoor ranges with smaller downrange impact areas. This can make it possible to conduct training in places where live firing would not be possible (for safety or regulatory reasons) if firing the original full-power ammunition.
With shotguns, the smaller shot load carried by a smaller shell increases the challenge of hitting targets, and therefore can be used as a handicap for a skilled shooter, or to increase difficulty when training.[14]
Some European conversions exist for special gallery cartridges, similar in concept to the
In media
- An episode of the television series Columbo[16] featured a "calibration converter," as it was called in the show. The killer had a large handgun collection in his office but none of them matched the .22 caliber of the bullet he used to kill the victim. Still, Columbo suspected the killer. To find out how he could have committed the murder, Columbo utilized subliminal cutsto get the killer to expose himself.
See also
- Cadet trainer
- Collet locking
- Glossary of firearms terms
- List of established military terms
- Military education and training
- Weapon effects simulation
- Range-finder painting
References
- National Rifle Association of America: 48.
- ^ Venturino, Mike. "Springfield M1 Garand .308". Shooting Times. Archived from the original on 2009-02-17. Retrieved 2012-05-01.
- ^ "Caliber Conversions". Numrich Gun Parts Corporation. Retrieved 20 April 2016.
- ^ "Same Gun, Different Cartridges". Riflemagazine.com. Retrieved 2012-05-01.
- ^ "Insert Barrels For Rifles And Single Shot Pistols!". Mcace.com. Archived from the original on 2012-05-10. Retrieved 2012-05-01.
- ^ "Our Complete Line Of Shotgun Inserts To Increase The Versatility Of Your Shotgun". Mcace.com. Archived from the original on 2012-04-21. Retrieved 2012-05-01.
- ^ "Chamber Mates Sub Gauge Shotgun Chamber inserts Patterns & Velocity". Chambermates.com. Retrieved 2012-05-01.
- ^ "Companion Drop-In .410 Bore Tube Set, UltraLite - COMP410ULT". Briley.com. Archived from the original on 2007-09-28. Retrieved 2012-05-01.
- ^ "Jonathan Arthur Ciener, Inc. Gun Conversions".
- ^ "Marvel Precision".
- ^ Rick Breneman (24 July 2011). "COLT ACE, SERVICE ACE & CONVERSIONS".
- ^ Dick Culver. "The Pipsqueak Pistol That Never Was..." Civilian Marksmanship Program. Archived from the original on 2008-07-25.
- ^ Willis, Andrew. "Rifle Chamber Insert (Converts rifles to fire pistol cartridges)". Guns and Shooting Online. ChuckHawks. Retrieved 20 April 2016.
- ^ "Shooting Subgauge Loads". Shotgunreport.com. Archived from the original on 2012-02-07. Retrieved 2012-05-01.
- ^ "The Cartridge Collector". Oldammo.com. Retrieved 2012-05-01.
- ^ Television episode "Double Exposure" of "Columbo" series. Season 3, Episode 4, originally aired December 16, 1973.