.25 Automatic / .25 ACP (using Hornady bullets)
Date: Aug 14 2014
The .25 Automatic (aka .25 ACP or 6.35mm) was originally developed in Europe around 1902 for the FN/Browning "Baby" Model. U.S. guns manufactured for this cartridge first appeared in the Colt Vest Pocket Model 1908 Hammerless (also of Browning design), which was very similar to the FN Baby Model. In the years since, the list of companies, both foreign and domestic, that have manufactured guns is lengthy.
Factory ammunition has traditionally been loaded with a 50-grain FMJ bullet at an advertised 760 fps; however, in recent years 35-grain JHP bullets have become popular and are generally advertised at 900 fps. In the Browning/FN test pistol Winchester and Remington 50-grain FMJ loads averaged 744 fps and 751, respectively, while Hornady’s 35-grain XTP clocked 798 fps, all of which were easily duplicated through handloading.
The most difficult part in handloading for the .25 Automatic is in handling the tiny cases. Due to its very small case capacity, great care should be taken to make certain that the powder charges are exact. In some instances, 62 fps average velocity increases were seen when powder charges were increased just .01 grain. Only use an accurate and best quality scale.
If powder charges are to be thrown, the powder measure should have an extremely small cavity and be designed to throw accurate charges that hover around 1.0 grain. The finest grain powders will give the most uniform thrown charge weights, with particularly good results being obtained with Accurate No. 2 powder in the Redding Competition Model 10X powder measure, which displayed less than .01 grain variance.
A taper crimp should be applied, with SAAMI specifications calling for .278 inch. However, in checking factory loads from several manufacturers, case mouth crimp measured between .272 and .275 inch. In developing the accompanying data Winchester cases were used exclusively and were crimped .273 inch at the case mouth.
Industry maximum average pressure is 25,000 psi, with none of the accompanying data exceeding that figure. Some published "starting loads" may fail to cycle in some pistols.