.410 bore

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.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 revolvers chambered in that caliber to fire shot without any modifications.

1 Naming
2 Uses
3 Survival arms
4 External links

[edit] Naming

The .410 caliber is a bore and not a gauge because the barrel diameter is .410 inches (10.4 mm); a true gauge is a measurement of the number of lead balls of bore diameter that constitute a pound (454 gram). The .410, when measured by gauge, is a 67 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). .410 is the only popular shotgun cartridge named by bore rather than gauge, leading to some confusion.

[edit] 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 competitive shooters choose the .410 bore because of the challenge it presents; .410 bore guns generally have full chokes to form a tight pattern with the small load of shot, and this makes hitting moving targets very challenging.

The .410 bore is also commonly used for small game animals such as squirrel and rabbit. Some shooters however do discourage the use of the .410 as an introduction for young shooters as the negligible recoil does not familiarize the beginners with the heavier recoil of say, a 12 gauge, but mostly because of the difficulty in hitting moving targets as mentioned above.

The American Derringer corporation markets a 3-inch .410 shell filled with five balls of 000 buckshot for self defence purposes.

[edit] 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 guns, 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 12 inch barrel, the same length as the stock, and folds in half for storage, making a compact package. This is classified as a sawed-off shotgun, so 18 inch barrelled models are made for civilian sales. 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.