|Place of origin||United States|
|Parent case||.45 ACP|
|Case type||Rimless, bottleneck|
|Bullet diameter||.357 in (9.1 mm)|
|Base diameter||.470 in (11.9 mm)|
|Rim diameter||.471 in (12.0 mm)|
|Rim thickness||.050 in (1.3 mm)|
|Case length||.880 in (22.4 mm)|
|Overall length||1.22 in (31 mm)|
|Primer type||large pistol|
It is essentially a .45 ACP case, necked down to .357, resulting in a cartridge similar in form to the earlier 7.65×21mm Parabellum and 7.63×25mm Mauser cartridges. It was created to be a low recoil target cartridge that would function reliably with multiple bullet types, FMJ to cast lead wadcutters without the feeding problems that straight walled pistol rounds sometimes exhibit. The cartridge can be used in standard .45 ACP magazines.
.45 ACP cases can be resized to handload .38/.45 Auto cartridges  using form and sizer dies still available from the RCBS Corporation, p/n 56468.
Nearly any M1911 pistol and pistols of the same pattern can be converted to the .38/.45 cartridge with a replacement barrel, from a 38 Super barrel reamed out to .38/.45 dimensions. During the round's initial popularity, drop-in barrels were available from makers like Bar-Sto.