Gas check
A gas check is a gasket type component of
jacketed bullets are used in high pressure cartridges. The use of a gas check inhibits the buildup of lead in the barrel and improves accuracy.[1]
Construction
Gas checks are most commonly found in the form of a thin cup or disc made of a ductile metal.
swaging
.
Purpose
High pressures, such as those commonly encountered in maximum loadings of magnum
obturates to provide a seal and prevents the propellant gas leakage that causes gas cutting, and helps the bullet grip the rifling.[1][2][3][4][5]
While most commercial cartridges operating at high pressure use jacketed bullets, gas checked bullets are popular with
recycle lead to make cast bullets, and then must only pay for the gas check. Custom lead bullets, such as those for obsolete calibers, wildcat cartridges
, or for special purposes, are easily made with inexpensive casting or swaging equipment. In contrast, manufacturing jacketed bullets requires far more expensive equipment to draw the jackets and swage in the core, so is generally limited to commercial projectile producers. As a result, although it is possible for hobbyists to manufacture jacketed bullets, many of them take the easier option and use gas checked bullets instead.
Cartridges commonly using gas checks
The most common use of gas checks are found in
black powder with large charges of smokeless powder, velocities well in excess of 1000 ft/s (300 m/s) were produced from handguns for the first time. At these velocities and pressures traditional soft lead bullets would quickly foul the barrel with lead deposits, so gas checked bullets were used in these experimental cartridges.[3]
The other common use of gas checked bullets is in obsolete military rifles. Many of these rifles used calibers that were unique to the rifle; low levels of commercial production and dwindling supplies of surplus ammunition quickly result in high ammunition prices. Many of these rifles use unusual bore diameters; for example, both the British
full metal jacket bullet design in the weight used by the military loading. Custom made bullets also allow the bullet to be carefully sized to match the bore, which can vary considerably in surplus rifles, and provide both more accuracy and more flexibility. Gas checks allow these bullets to be pushed to higher velocities without undue fouling of the barrel and attendant problems.[2]
See also
References
- ^ a b "GunTec Dictionary, gas check". Archived from the original on 2011-07-14.
- ^ a b NEI Handtools (archived) information on bullet molds, with information on variations in bore size and how it impacts leading
- ^ a b Classic Cast Bullets Guns Magazine, Oct, 2001, by John Taffin
- ^ Montana Bullet Works Archived 2014-04-02 at the Wayback Machine FAQ, with information on when to use a gas check
- ^ The Los Angeles Silhouette Club reference on cast bullets