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« ตอบ #2 เมื่อ: สิงหาคม 20, 2012, 08:52:45 PM » |
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In 1956, the U.S. Air Force adopted the Cartridge, Caliber .38, Ball M41, a military variant of the .38 Special cartridge designed to conform to the rules of land warfare.
The original .38 M41 ball cartridge used a 130-grain full metal jacketed bullet, and was loaded to an average pressure of only 13,000 psi,
giving a muzzle velocity of approximately 725 ft/s (221 m/s) from a 4-inch (100 mm) barrel.
This ammunition was intended to prolong the life of S&W M12 and Colt Aircrewman revolvers equipped with aluminum cylinders and frames,
which were prone to stress fractures when fired with standard .38 ammunition.
By 1961, a slightly revised M41 .38 cartridge specification known as the Cartridge, Caliber .38 Ball, Special,
M41 had been adopted for U.S. armed forces using .38 Special caliber handguns.
The new M41 Special cartridge used a 130-grain FMJ bullet loaded to a maximum allowable pressure of 16,000 psi for a velocity of approximately 950 ft/s (290 m/s)
in a solid 6-inch (150 mm) test barrel, and about 750 ft/s (230 m/s) from a 4-inch (100 mm) revolver barrel.
The M41 ball cartridge was first used in .38 revolvers carried by USAF aircrew and Strategic Air Command security police,
and by 1961 was in use by the U.S. Army for security police, dog handlers, and other personnel equipped with .38 Special caliber revolvers.
A variant of the standard M41 cartridge with a semi-pointed, unjacketed lead bullet was later adopted for CONUS (Continental United States) police and security personnel.
At the same time, .38 tracer cartridges were reintroduced by the US Navy, Marines, and Air Force to provide a means of emergency signaling by downed aircrew.
Tracer cartridges in .38 Special caliber of different colors were issued, generally as part of a standard aircrew survival vest kit.
A request for more powerful .38 Special ammunition for use by Air Police and security personnel resulted in the Caliber .38 Special, Ball,
PGU-12/B High Velocity cartridge. Issued only by the U.S. Air Force, the PGU-12/B had a greatly increased maxiumum allowable pressure rating of 20,000 psi,
sufficient to propel a 130-grain FMJ bullet at 1,125 ft/s (343 m/s) from a solid 6-inch (150 mm) test barrel,
and about 950-980 ft/s from a 4-inch (100 mm) revolver barrel.
The PGU-12/B High Velocity cartridge differs from M41 Special ammunition in two important respects - the PGU-12/B is a much higher-pressure cartridge,
with a bullet deeply set and crimped into the cartridge case.
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