The 7mm IHMSA
By Chuck Hawks
The legendary Elgin Gates developed several wildcats for silhouette competition. Among the best known of those is the 7mm IHMSA (International Handgun Metallic Silhouette Assn.).
The sport of handgun silhouette shooting has been responsible for the development of a number of wildcat cartridges intended for use in single shot pistols. Most of these are rifle type cartridges based on bottleneck cases, not traditional straight cased pistol cartridges.
The 7mm IHMSA is a big, powerful pistol cartridge based on a necked-down .300 Savage case. This is a rimless, bottleneck case. Its dimensions are as follows: .473" rim diameter, .471" head diameter, .446" shoulder diameter, 38 degree shoulder angle, .312" neck diameter, 1.866" case length, and 2.67" overall cartridge length. It uses standard .284" (7mm) bullets.
The sixth edition of the Hornady Handbook of Cartridge Reloading lists 7mm IHMSA loads for bullet weights from 120 grains to 162 grains. It shows that a minimum charge of 36.9 grains of W748 powder behind a 139 grain Hornady bullet gives a MV of 2200 fps from the 15" pistol barrel. A maximum charge of 40.6 grains of W748 gives a MV of 2500 fps. These loads were developed in a Wichita pistol and used IHMSA cases and Federal 210 primers.
No only does the 7mm IHMSA reliably topple steel rams, it is a potent hunting cartridge that gives rifle-like performance in single shot pistols such the bolt action Wichita and Weatherby. Of course, those pistols are essentially short barreled rifles with the butt stock removed.
Copyright 2006, 2014 by Chuck Hawks. All rights reserved.