what's the difference between 380 acp and 380 auto
.380 ACP The .380 ACP (9×17mm) (Automatic Colt Pistol) is a rimless, straight-walled pistol cartridge developed by firearms designer John Moses Browning. The cartridge headspaces on the mouth of the case.[2] It was introduced in 1908 by Colt, for use in its new Colt Model 1908 pocket hammerless semi-automatic, and has been a popular self-defense cartridge ever since, seeing wide use in numerous handguns (typically smaller weapons). Other names for .380 ACP include .380 Auto, 9mm Browning, 9mm Corto, 9mm Kurz, 9mm Short, 9×17mm and 9 mm Browning Court (which is the C.I.P. designation). It should not to be confused with .38 ACP, from which it was developed.[3]
.300 AAC Blackout The .300 AAC Blackout (designated as the 300 BLK by the SAAMI[1] and 300 AAC Blackout by the C.I.P.[2]), also known as 7.62×35mm is a carbine cartridge developed in the United States by Advanced Armament Corporation (AAC) for use in the M4 carbine. Its purpose is to achieve ballistics similar to the 7.62×39mm Soviet cartridge in an AR-15 while using standard AR-15 magazines at their normal capacity. It can be seen as a SAAMI-certified copy of J. D. Jones' wildcat .300 Whisper. Care should be taken not to use 300 BLK ammunition in a rifle chambered for 7.62×40mm Wilson Tactical.[3]