The .45 ACP (Automatic Colt Pistol) or .45 Auto is a cartridge caliber developed by John M. Browning for the Colt M1911. The .45 designation refers to hundredths of an inch, which corresponds to a bullet diameter of 11.43 mm. The metric designation of the ammunition is 11.43x23mm. It is called 11.25mm in Argentina and Norway. This ammunition is mainly used in the United States where it is a solid tradition. Many pistols and some submachine guns are chambered for this ammunition.
Derived from the .38 ACP, it responded to the express request of the American cavalry who had tested 9 mm caliber revolvers in the early 1900s to replace their models chambered in .45 Colt (often wrongly named .45 Long Colts). Colt and Browning were working in 1904 on a weapon chambered in .41, i.e. a caliber of about 10 mm, which they declined in 1905 in .45 at the request of the cavalry. The first ammunition, comprising a 13 g bullet animated with an initial speed of 275 m/s, quickly gave way to a 15 g bullet at 260 m/s.
The .45 ACP because of its heavy and slow bullet causes a recoil (that is to say a quantity of movement) important compared to the kinetic energy which it develops. Its large diameter limits weapon capacity (the Colt M1911 holds only 7 rounds) and requires more production resources, which is a significant disadvantage in wartime. Its low velocity was a major drawback during the Second World War because it limited the range of American submachine guns such as the M1 and the M3A1 to around fifty meters, i.e. a reach approximately half that of the MP40 used by the enemy. .
However, the importance of its caliber and its moderate power have several advantages:
* its large-diameter projectile transmits, at the same expansion rate, more energy to the target than a smaller caliber. This increases the chance of damaging a vital organ, which translates to good stopping power
* its moderate power does not cause significant muzzle flames and detonation,
* it develops a lower chamber pressure than other handgun ammunition, therefore it is gentle on the weapon and the shooter (by causing less violent recoil than comparable ammunition)
* it reduces the ability of the projectile to pass through the target of the bullets expanding there only slightly.
True American tradition, it is in competition with the 9 mm Parabellum which tends to impose itself in the armies. The US Army abandoned the venerable Colt M1911 for the M9 during the 1980s, following which many special units re-adopted weapons chambered in .45 ACP.
Derivatives
The .45 Auto gave birth to other ammunition:
* the .451 Detonics (supercharged version),
* the .45 HP (version with a case shortened by one millimeter, created to circumvent the laws in Italy),
* the .45 GAP (version with shortened case and total length, created by Glock to be usable in compact weapons),
* the .454 Casull "Magnum" version of the classic .45.
Technical data
The characteristics of this ammunition vary according to the loads and the type of bullets used. The standard military ammunition has the following characteristics:
* Bullet:armored warhead (FMJ - Full Metal Jacketed)
* Metric designation:11.43 x 23 mm
* Bullet mass:15g
* Mass of the cartridge:21.5 g
* Initial speed:260 m/s