Editing .410 bore

'''.410 bore''', commonly misnamed the '''.410 gauge''', is the smallest [[caliber]] of [[shotgun shell]] commonly available.  It has similar base dimensions to the [[.45 Colt]] [[revolver]] cartridge (though the .410 is significantly longer, up to 3 inches in length), allowing many [[single-shot]] firearms and some [[revolver]]s chambered in that caliber to fire shot without any modifications.

[[Image:Shotshell 001.jpg|thumb|300px|From left to right; a [[.45 ACP]], a .410 Bore Shotshell, a [[20 gauge]] shotshell, and a [[12 gauge]] shotshell.]]
==Origin== 
The .410 bore is a relative latecomer in shotgun sizes.  It appears to have become popular around 1900.  Some suspect that this shotgun arose from converted rifles of a similar bore diameter.  The first ammunition was two inches (5.08 cm) in length, compared with the modern 2.5 and 3.0 inch sizes. 

==Naming==
Pronounced ''four-ten'', the .410 shotgun is a ''bore'' and not a ''gauge'' because the barrel diameter is .410 inches (10.4 mm); a true [[gauge (shotgun)|gauge]] is a measurement of the number of lead balls of bore diameter that constitute a pound (454 grams). The .410, when measured by gauge, would be around 67 or 68 gauge,<ref>Barnes, Frank C. (2006) [1965]. Skinner, Stan. ed.. ''Cartridges of the World'' (11th Edition ed.). Iola, WI, USA: Gun Digest Books. p. 502. ISBN 0-89689-297-2.</ref>, not the sometimes mistakenly assigned 36 gauge.  A true gauge measuring .410 would have a 2.25 inch (57 mm) bore; a 410 gauge would measure .225 inches (5.7 mm).  In the US, the .410 is the only popular shotgun cartridge named by bore rather than gauge, though it is often referred to as a ''four-ten gauge''.  In the [[United Kingdom]] and other English speaking countries, all shotgun sizes are called ''bore'', whether measured by gauge or bore diameter.

==Uses==
As the smallest of traditional [[shotgun]] sizes, .410 bore guns throw the least weight of shot.  This results in a very low [[recoil]], so the .410 is often chosen for young shooters, who might have problems with a heavier recoiling shotgun. Some shooters however do discourage the use of the .410 as an introduction for young shooters, both because the negligible recoil does not familiarize the beginners with the heavier recoil of larger cartridges such as the 12 gauge, and because of the difficulty in hitting moving targets with the small charge of shot used by the .410.

Some competitive shooters choose the .410 bore because of the challenge it presents; .410 bore guns generally have full [[Shotgun#Pattern and choke|chokes]] to form a tight pattern with the small load of shot, and this makes hitting moving targets very challenging.  By using [[caliber conversion sleeve|sub-gauge inserts]], a 12 gauge [[break action|break open action]] can be temporarily converted down as far as a .410 bore to provide additional challenge when training, or to handicap the shooter.

The .410 bore is also commonly used for small game animals such as squirrels and rabbits, where the small diameter patterns of a full choke are less problematic than with birds.

The .410 bore is considered far inferior to the traditional 12 gauge shotshell for defensive use<ref>[http://www.chuckhawks.com/ammo_by_anonymous.htm Chuck Hawks'] updated rec.guns FAQ on defensive ammunition</ref>, though a number of companies market defensive guns chambered in .410, such as the [[Mossberg 500]] ''Home Security'' model.  Defensive ammunition is harder to find, since most .410 bore shells are loaded with birdshot.  American Derringer and Winchester market .410 bore 000 buckshot with 5 pellets in 3 inch and 3 in 2.5 inch shells<ref>[http://winchester.com/products/catalog/shotlist.aspx?use=4&gauge=410 Winchester] .410 buckshot</ref><ref>[http://www.amderringer.com/safe.html American Derringer] .410 buckshot</ref>, compared to the 10 pellets in a 3 inch 12 gauge, or twelve 00 pellets in a 2¾ inch 12 gauge.  With [[shotgun slug|slug]] loads, the .410 bore compares better, with about 750 ft·lbf (1,020 J) of muzzle energy, comparable to a [[.44 Magnum]] [[handgun]] loading<ref>[http://www.federalcartridge.com/ Federal] .410 bore slug #F412RS, 762 ft·lbf (1,033 J), vs. .44 Magnum #P44HS1, 780 ft·lbf (1,058 J)</ref>.

==Survival arms==
The small size of the .410 bore makes it popular for use in compact firearms carried for emergency use.  Commonly these are [[combination gun]]s, with a [[.22 Hornet]] or .22 [[rimfire]] rifle barrel mounted over a .410 bore shotgun barrel.  The most famous of these is the [[M6 survival rifle]] made by [[Springfield Armory, Inc.]] for the US Air Force, and a number of copies are made by other makers.  The original has a 14 inch barrel, the same length as the stock, and folds in half for storage, making a compact package.  With the short barrel, this is classified as a [[sawed-off shotgun]] in the United States, so 18.5 inch barrelled models are made for civilian sales, as well as a 16 inch pistol version in .22 over .45 Colt.<ref>S. P. Fjestad. ''{{Amazon/Blue Book}}, 13th Ed.''. Blue Book Publications.</ref>  Special flare cartridges in .410 were issued with the USAF model.

The [[Thompson Center Arms]] Contender pistols are commonly encountered with a special .45 Colt/.410 bore barrel.  The barrel is rifled for the .45 Colt, but has a special choke and vent rib to make it function as a shotgun.  Due to the rifled barrel, the assembled firearm is considered a rifle or pistol (depending on barrel length) and thus is not subject to the [[National Firearms Act]] 18 inch minimum barrel length.<ref>[http://www.tcarms.com/firearms/g2ContenderPistols.php G2 Contender Pistols]</ref>

==Handguns==
The fact that the .410 bore shell fits in a [[.45 Colt]] chamber has resulted in some unusual applications.  While shotguns are often [[sawed-off shotgun| limited in minimum length]], a firearm chambered in .45 Colt, such as the Contender pistol, is not defined as a shotgun even though it can chamber shotgun shells.  American Derringer has long offered .45 Colt/.410 bore [[Derringer]]s<ref>[http://www.amderringer.com/m1.html American Derringer model 1]</ref>, and recently [[Taurus]] and [[Magnum Research]] both began to offer revolvers with extended cylinders, chambered for .45 Colt but long enough to hold .410 shells as well.  Magnum Research's is an expensive single-action model in their [[Magnum Research BFR|BFR]] (Biggest, Finest Revolver) line, while the inexpensive Taurus model is similar in price to their other double-action revolvers.

==References==
<references/>
* [http://everything2.com/e2node/.410%2520bore .410 bore] 
==External links==
*[http://www.shotgunreport.com/Reviews/Remington/Rem28_410.html The Shotgun Report] review of the [[Remington 870]] in 28 gauge and .410 bore
* "[http://www.chuckhawks.com/410bore.htm The .410 Bore]" by Chuck Hawks
* "[http://www.chuckhawks.com/410_what_good.htm The .410: What Good Is It?]" by Randy Wakeman
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[[Category:Shotguns]]
[[category:.410 firearms]]
[[category:ammunition]]