Above Picture on Right Side for Size Comparison: Left .300 RCM, Right .375 Ruger (the parent case for the 300 RCM and 338 RCM see below).
One Cartridge, not a box: .300 RCM (RCM for Ruger Compact Magnum) by Hornady, factory loaded with new Hornady brass cases with the “HORNADY 300 RCM” Head-Stamp and loaded with a 150 grain SST or PCJHP (Plastic Covered Jacketed Hollow Point) projectile.
History of the .300 RCM Cartridge:
.300 RCM for Ruger Compact Magnum and the large diameter .338 RCM (see below)where developed by shorting and reducing the diameter of the .375 Ruger was introduced in 2008 for use in the Ruger Model 77 bolt-action rifle.
The idea of shortening a magnum case, and increasing performance by optimizing a case’s geometry to deliver more power with less powder began with Lazzeroni back in the early 1990’s, ansd then Winchester introduced 7 different Short and Super Short Magnums, (3 WSSM & 4 WSM) in the early 2000’s and Remington has the 7mm and .300 SAUM (Short Action Ultra Magnum).
Both Winchester and Remington produced their Short Action Magnums by shortening and necking down the .404 Jeffery case, however Ruger produced the .300 and .338 RCMs by shortening and necking down the .375 Ruger Case.
