Starline 45 Auto Brass Cases 100ct 45 Auto Brass (Large Pistol primer)45 ACP, 45 Automatic, 45 Automatic Colt Pistol0.892 - 0.897 O.A.L. .45 Auto Brass: Designed by John Browning, the .45 Auto, or .45 ACP, has been adopted at one point or another by several governments as their official military handgun chambering. It is still popular in the U.S. as a personal defense or target gun. 100 count by weight