.380 Auto (ACP) (using Sierra bullets)
Date: Feb 23 2021
The .380 Automatic (aka .380 ACP) was introduced around 1908 and was designed by John Browning for the Colt Pocket Automatic Pistol. In the past century it has been chambered for many different guns and is popular throughout the world. Today it has found renewed popularity in compact, concealed-carry pistols.
In spite of serving primarily as a defense cartridge, it has proven capable of outstanding accuracy when chambered in target pistols. During testing, extreme spreads were often less than 10 fps for a 10-shot string.
Bullets should be seated to the correct cartridge overall length, then taper crimped as a separate step. The crimp should measure a maximum of .373 inch at the case mouth. In referencing many factory loads, crimps measured .3695 to .3705 inch, which holds the bullet firmly in place but also serves for positive headspace control. All loads were crimped to .370 inch.
Due to the unusually short case and powder column, seating bullets deeper than listed will cause pressures to increase, sometimes substantially, so is generally not recommended.
All loads here are within industry pressure limits that are currently established at 21,000 psi.