The .45 Auto Rim
 

Nation	Year	Max. press.
U.S.A.	1920 (?)	22000psi

This rather obscure round was the answer to a problem which had already been solved. It is essentially a .45 A.C.P. cartridge with a rim for use in the M1917 revolvers. What is so strange about this is that those revolvers were specifically designed to eliminate logistics problems for the army, by using the same ammunition as the .45 auto. This presents certain problems in a revolver because revolver cartridges use a rim to extract, whereas autos use a grove. The solution to this was to clip the cartridges together in a so called "half moon clip" which would allow the ejector to empty the cylinder. This meant that the space between the cylinder and the frame had to be rather large. The .45 auto rim was an attempt to create a cartridge that could be fired in these guns without the use of a half moon clip. The problem with this is that a very thick rim is required because of the gap between the frame and the cylinder. Even worse, a half moon clip is much handier, and quicker than loading individual rounds. These two factors, along with the abundance of .45 ammo, brass, etc. have conspired to keep this round from ever achieving much popularity. Internally the case is that of the .45 A.C.P. The pressure limit is also the same, meaning that load data for the two rounds are identical with one exeption---thre are no +P or super rounds for the .45 Auto Rim.