The .45 ACP (Automatic Colt Pistol) was 
adopted for use by the U.S.  military in 1911, in 
the semi-Automatic M1911 Colt-developed pistol of 
8 rounds capacity (7 in the magazine and 1 
chambered).  While the handgun was to undergo 
many significant improvements in 1926 and emerge 
as the legendary M1911A1, the cartridge would 
continue unchanged.

    The .45 ACP thus began the longest military 
career of any cartridge to date, both pistol and 
cartridge being replaced by the M92 Beretta and 
9mm Parabellum NATO-standard in 1985.  The 
commercial use of the cartridge has even 
increased since it's "discharge" from the 
military.

    The military cartridge uses a 230-grain 
round-nosed jacketed bullet, yielding 855 fps at 
25 ft. from the muzzle.  The commercial version 
is only slightly below that, but otherwise 
identical.  The popular name for this ammunition 
is "hardball".

    The .45 ACP is a favorite defense round due 
to it's power.  The NRA Handloader's Manual 
recommends virtually any bullet design other than 
the hardball load for this purpose.  It also 
suggests that hardball loads are less accurate 
than either jacketed hollow-points or 
semi-wadcutters.