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53-483: The M6 is also available with "X Caliber" adapter sleeves that fit inside the shotgun barrels, allowing it to fire a wide range of handgun, rifle, and shotgun ammunition. The Chiappa M6 is marketed to "outdoorsmen, ranchers, pilots or anyone who needs a portable, rugged and reliable rifle/shotgun combination." It has a skeletonized metal buttstock that surrounds a polypropylene foam insert. The buttstock has cutouts for two shotgun shells, five .22 rimfire cartridges, and

106-419: A magazine , though they will not provide sufficient energy to cycle an automatic action. 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

159-496: A rifled barrel, the distance is measured between opposing lands or between opposing grooves ; groove measurements are common in cartridge designations originating in the United States , while land measurements are more common elsewhere in the world. Measurements "across the grooves" are used for maximum precision because rifling and the specific caliber so measured is the result of final machining process which cuts grooves into

212-692: A " 30 caliber rifle", which could accommodate any of a wide range of cartridges using a roughly 0.30 inches (7.6 mm) projectile; or as a "22 rimfire", referring to any rimfire firearms firing cartridges with a 22 caliber projectile. However, there can be significant differences in nominal bullet and bore dimensions, and all cartridges so "categorized" are not automatically identical in actual caliber. For example, 303 British firearms and projectiles are often "categorized" as ".30-caliber" alongside several dozen U.S. "30-caliber" cartridges despite using bullets of .310–.312-inch (7.87–7.92 mm) diameter while all U.S. "30-caliber" centerfire rifle cartridges use

265-405: A .250 inch land diameter and .257 inch groove diameter. The .308 Winchester is measured across the grooves and uses a .308-in diameter (7.82-mm) bullet; the military-specification version is known as 7.62 × 51 mm NATO , so called because the bore diameter measured between the lands is 7.62 mm, and the cartridge has a case 51 mm long. Converting a rifle to fire a different cartridge in

318-455: A US " 45 caliber " firearm has a barrel diameter of roughly 0.45 inches (11.43mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa. In

371-447: A cleaning kit. The design allows it to fold in half for more compact stowage. The shotgun barrels use interchangeable Remington-type choke tubes ("Rem-Choke") and each barrel has its own trigger. It uses a lever-action to cock the internal hammers and open the action. It has a tang safety located at the top rear (or "tang") of the receiver. It uses an M1 carbine -type rear sight and a fiber optic front sight. It also has Picatinny rails on

424-412: A common, standard .308-inch (7.82 mm) bullet outside diameter. Using bullets larger than design specifications causes excessive pressures, while undersize bullets cause low pressures, insufficient muzzle velocities and fouling that will eventually lead to excessive pressures. Makers of early cartridge arms had to invent methods of naming cartridges since no established convention existed then. One of

477-583: A different definition may apply , caliber (or calibre ; sometimes abbreviated as " cal ") is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters . In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example,

530-432: A distance of 26 mi (42 km). Smoothbore cannon and carronade bores are designated by the weight in imperial pounds of spherical solid iron shot of diameter to fit the bore. Standard sizes are 6, 12, 18, 24, 32, and 42 pounds, with some non-standard weights using the same scheme. See Carronade#Ordnance . From about the mid-17th until the mid-19th century, the measurement of the bore of large gunpowder weapons

583-513: 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 .22 Hornet . A notable exception to this is the Thompson Center Arms Contender, which has both centerfire and rimfire firing pins which can be selected with

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636-414: A handful of the devices were destroyed by the military. 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

689-443: 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. Sleeves that exceed the chamber length are generally used in break open actions, which allow easy insertion and removal. Like supplemental chambers, caliber conversion sleeves completely surround

742-592: A multiple of the bore diameter. For example, a 4-inch gun of 50 calibers would have a barrel 4 in × 50 = 200 in long (written as 4" L/50 or 4"/50). A 16-inch gun of 50 calibers (16" L/50) has a barrel length of 50 × 16 = 800 inches (66 ft 8 in). Both 14-in and 16-in navy guns were common in World War II. The British Royal Navy insisted on 50-cal guns on ships as it would allow 1,900 to 2,700 lb (860 to 1,220 kg) shells to travel at an initial velocity of up to 1,800 mph (2,897 km/h) to

795-503: A new upper assembly and magazine. Conversions for .22 caliber centerfire rifles and carbines such as the AR-15 and Mini-14 consist of a magazine and an insert that replaces the bolt and includes a cartridge conversion insert that goes into the chamber. Conversions for rifles and carbines of larger caliber, such as the AK-47 or Thompson submachine gun include a rifled insert barrel extending beyond

848-482: A pound; therefore, its barrel is smaller than the 12-gauge. This metric is used in Russia as "caliber number": e.g., "shotgun of the 12 caliber." The 16th caliber is known as "lordly" ( Russian : барский ). While shotgun bores can be expressed in calibers (the .410 bore shotgun is measured as .410 in (10.4 mm) in diameter, unlike with rifles the actual bore diameter of a smoothbore shotgun varies significantly down

901-432: A related expression. The gauge of a shotgun refers to how many lead spheres, each with a diameter equal to that of the bore, that amounts to one pound (454 g (1.0 lb)) in weight. In the case of a 12-gauge (18.5 mm) shotgun, it would take 12 spheres the size of the shotgun's bore to equal a pound. A numerically larger gauge indicates a smaller barrel: a 20-gauge (15.6 mm) shotgun requires more spheres to equal

954-546: A shorter cartridge of similar base diameter. A supplemental chamber or cartridge adapter is typically used for a shorter cartridge of reduced diameter. 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 rifle or handgun cartridges may have rifled barrels. Additional variations may allow centerfire weapons to fire rimfire ammunition and/or retain autoloading function with

1007-464: 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

1060-461: 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

1113-495: Is based. The following table lists some of the commonly used calibers where both metric and US customary units are used as equivalents. Due to variations in naming conventions, and the whims of the cartridge manufacturers, bullet diameters can vary widely from the diameter implied by the name. For example, a difference of 0.045 in (1.15 mm) occurs between the smallest and largest of the several cartridges designated as ".38 caliber". Shotguns are classed according to gauge,

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1166-466: Is commonly used in military surplus arms such as the M1 Garand , allowing the use of often less expensive surplus military ammunition. 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

1219-419: Is much variance in the use of the term "small-bore", which over the years has changed considerably, with anything under 0.577 inches (14.7 mm) considered "small-bore" prior to the mid-19th century. While modern firearms are generally referred to by the name of the cartridge the gun is chambered for, they are still categorized together based on bore diameter. For example, a firearm might be described as

1272-715: 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. Supplemental chambers in .22 caliber, and potentially .17 caliber as well, pose

1325-413: The 20-gauge models to fire 9mm Luger, .38 Special/.357 Magnum, .45 ACP, and .45 Long Colt/.410 bore ammunition. These adapter sleeves are available separately and are compatible with any single- or double-barrel, 12- or 20-gauge break-action shotguns. This firearms -related article is a stub . You can help Misplaced Pages by expanding it . Caliber conversion sleeve A caliber conversion device

1378-422: The bore diameter and the length of the cartridge case; for example, the 6.5×55mm Swedish cartridge has a bore diameter of 6.5 mm and a case length of 55 mm. The means of measuring a rifled bore varies, and may refer to the diameter of the lands or the grooves of the rifling. For example, the 257 Roberts and 250 Savage both use a .257 inch projectile; both 250 Savage and 257 Roberts rifle bores have

1431-545: The bullet weight in grains was designated, such as 45-70-405. This scheme was far more popular and was carried over after the advent of early smokeless powder cartridges such as the 30-30 Winchester and 22 Long . Later developments used terms to indicate relative power, such as .44 Special and .44 Magnum . Variations on these methods persist today, with new cartridges such as the 204 Ruger and 17 HMR (Hornady Magnum Rimfire). Metric diameters for small arms refer to cartridge dimensions and are expressed with an "×" between

1484-629: The challenge of hitting targets, and therefore can be used as a handicap for a skilled shooter, or to increase difficulty when training. Some European conversions exist for special gallery cartridges , similar in concept to the .22 CB rounds, which use a primer but no gunpowder. These adapters were chambered for centerfire versions of these tiny rounds, such as the 4mm 4mm Übungsmunition cartridge. Gallery cartridges such as these were intended for use in indoor target practice, and are similar in power and report to an airgun . Caliber In guns , particularly firearms , but not artillery, where

1537-451: The contemporary English ( avoirdupois ) pound massed of approximately 454 g (1.001 lb). Thus, a French 32-pounder at the Battle of Trafalgar threw a shot with 1.138 kg (2.51 lb) more mass than an English 32-pounder. Complicating matters further, muzzle-loaded weapons require a significant gap between the sides of the tube bore and the surface of the shot. This is necessary so

1590-454: 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. 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

1643-531: The early established cartridge arms was the Spencer repeating rifle , which Union forces used in the American Civil War . It was named based on the chamber dimensions, rather than the bore diameter, with the earliest cartridge called the "No. 56 cartridge", indicating a chamber diameter of .56 in; the bore diameter varied considerably, from .52 to .54 in. Later various derivatives were created using

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1696-432: The end of their barrel life, whereby the rifling is worn down to a point where a rifle loses some of its accuracy , the choice to make a caliber or cartridge change is often done at the same time as when a new rifle barrel is fitted to the rifle by a gunsmith . There are a few important factors to consider when converting a rifle to a different caliber or cartridge. The action of the rifle should be long enough to contain

1749-478: The firearm from gas operation or recoil operation to a simple blowback operation . This typically involves replacing the firearm's bolt or slide with a lightweight part lacking the locking mechanism, and a reduced power spring. The magazine must also be replaced, and in the case of caliber conversions, often the barrel as well. Conversions for short recoil pistols, such as the M1911 , Glock , and Beretta 92 consist of

1802-413: 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

1855-421: The length of the barrel, with the use of chokes and back-boring. In the United Kingdom, "gauge" is referred to as "bore" and in the United States "bore" is referred to as "gauge", e.g. a "12-bore shotgun or 12-gauge shotgun" has a bore or gauge that can accommodate a lead sphere weighing 1/12th of a pound. The term caliber is used as a measure of length of artillery barrels from muzzle to breech, expressed as

1908-621: The length of the chamber. One exception to the use of a special lightweight bolt was the Colt Service Ace , offered as a complete pistol or as a conversion kit for the M1911. While still nominally a blowback conversion, the Service Ace used a special "floating" chamber in the barrel that acted like a gas operated firearm's piston, helping push the bolt back with more force than a typical .22 Long Rifle blowback action. This additional force allowed

1961-451: The most common sizes encountered, although larger, smaller and intermediate sizes existed. In practice, though, significant variation occurred in the actual mass of the projectile for a given nominal shot weight. The country of manufacture is a significant consideration when determining bore diameters. For example, the French livre , until 1812, had a mass of 489.5 g (1.079 lb), whilst

2014-526: The nature of shotguns, the implications of using an insert differ. Since shotgun shells are all straight walled, a change in chambering means a change in diameter of the shell. However, since subgauge inserts are designed to be used with shot, not slugs, the shotgun's barrel can continue to be used, with little or no impact on patterning. Many makers offer longer inserts, though due to the variations in shotgun bore diameters, these usually require custom manufacture. Rifled inserts are also available, to allow

2067-404: The new barrel. One manufacturer has a .40 caliber (10 mm) minimum diameter for these inserts 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. Inserts for shotguns are called subgauge inserts , and function in much the same manner as inserts for handguns or rifles. However, due to

2120-413: The new cartridge case, but cannot be ejected or fed from a magazine, so they only offer a single shot per barrel without manual extraction and reloading. 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

2173-426: The new cartridge, the magazine should also be able to hold the new cartridge, the bolt face should be the correct diameter and the extractor the correct size to hold the head of the new cartridge. The most common of these caliber conversions on rifles, are usually done to change from a parent cartridge to a new cartridge based on it, like when converting a rifle to a 6.5 mm Creedmoor from a 308 Winchester on which it

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2226-405: The projectile may be inserted from the mouth to the base of the tube and seated securely adjacent the propellant charge with relative ease. The gap, called windage , increases the size of the bore with respect to the diameter of the shot somewhere between 10% and 20% depending upon the year the tube was cast and the foundry responsible. The relationship between bore diameter and projectile weight

2279-402: The rough bore, leaving the "lands" behind. Good performance requires a concentric, straight bore that accurately centers the projectile within the barrel, in preference to a "tight" fit which can be achieved even with off-center, crooked bores that cause excessive friction, fouling and an out-of-balance, wobbling projectile in flight. Calibers fall into four general categories by size: There

2332-567: The same basic cartridge, but with smaller-diameter bullets; these were named by the cartridge diameter at the base and mouth. The original No. 56 became the .56-56, and the smaller versions, .56-52, .56-50, and .56-46. The 56–52, the most common of the new calibers, used a 50-cal bullet. Other black powder-era cartridges used naming schemes that appeared similar, but measured entirely different characteristics; 45-70 , 44-40 , and 32-20 were designated by bullet diameter to hundredths of an inch and standard black powder charge in grains . Optionally,

2385-504: The same bore diameter, often involves merely re-chambering the barrel to the new cartridge dimensions, if the rim diameter of the new cartridge matches that of the old cartridge. Converting a rifle to fire a different cartridge in a different caliber and bore as what it initially was, means that the barrel of the rifle will also need to be changed. Because many competitive precision rifle shooters often shoot thousands of rounds per year both for practice and competitions, and they more often reach

2438-459: The small .22 Long Rifle cartridge to cycle a standard weight slide, which made the pistol handle more like the standard .45 ACP version. Another cartridge conversion was the Pedersen device , which was designed to convert the bolt action Springfield 1903 Mark I into a 40 shot blowback semi-automatic firearm chambering a lengthened version of the .32 ACP cartridge. The 1903 Mark I differed from

2491-419: The smaller cartridge. 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

2544-478: The standard rifle in that it had a slot cut in one side of the receiver, which served as an ejection port for the Pedersen device. The Pedersen device replaced the bolt of the 1903, and loaded from a magazine inserted from the top right of the receiver. Intended as a "secret weapon", the device was not ready for issue before the end of World War I , and it was eventually declared obsolete without being issued, and all but

2597-420: The top and sides for mounting a variety of accessories. The Chiappa M6 is available with "X Caliber" adapter sleeves . The X Caliber consists of eight adapter sleeves that allow the 12-gauge models to fire .380 ACP , 9mm Luger , .38 Special / .357 Magnum , .40 S&W , .44 Special / .44 Magnum , .45 ACP , .45 Long Colt / .410 bore , and 20 gauge ammunition. There are also four adapter sleeves that allow

2650-443: The turn of a switch, and does not require a centerfire to rimfire converter. The Hammond Game Getter works around this problem in its sleeves for .22 rimfire by creating an eccentric chamber that places the rim of the .22 cartridge in the center of the original chamber, thus allowing the firing pin to strike it directly. Since the supplemental chambers are approximately the size of a normal loaded cartridge, they will usually feed from

2703-407: The unrifled adapter. 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

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2756-536: The use of handgun cartridges or relatively low-power rifle cartridges such as the 12 gauge X Caliber adapter sleeves. Conversions for automatic firearms are often more complex than those for single shot or manual repeaters, as the difference in power available to the operating mechanism can be significant. There are a number of makers of cartridge conversions that convert various centerfire firearms to .22 Long Rifle , operating both as cartridge conversions and caliber conversions. These conversions typically convert

2809-444: Was usually expressed as the weight of its iron shot in pounds . Iron shot was used as the standard reference because iron was the most common material used for artillery ammunition during that period, and solid spherical shot the most common form encountered. Artillery was classified thereby into standard categories, with the 3-pounder, 4-pounder, 6-pounder, 8-pounder, 9-pounder, 12-pounder, 18-pounder, 24-pounder, and 32-pounder being

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