Ever since we built our first .300 Norma Magnum, we’ve been thinking on a cool wildcat to make from the case. 7mm was a likely bore diameter choice, as our intention was make something that could launch the current crop of high BC 7mm projectiles to screaming speeds and reliably feed from an AI pattern magazine. Our 7-300 Norma Improved does just that.
7-300 Norma Improved with 183gr SMK at 3.680″ OAL, shown with .308 Win at left for comparison.
The fireformed case has a capacity of approximately 107 grains, and in a 30″ barrel the cartridge is capable of producing velocities of 3300FPS with 175-183 grain bullets. The 195 Berger EOL can be driven to over 3200 FPS as well. The new 183 grain MatchKing HPBT from Sierra performs extremely well in this cartridge for long range steel killing and management hunting. Our longest kill to date with the 183SMK is 1355 yards on an aoudad. The case shoulder is improved to a 30 degree shoulder angle, which allows the cartridge to still feed well from a detachable magazine while also minimizing case stretch and working against premature throat erosion. Recommended powders for the 7-300 Improved are Hodgdon Retumbo and Vihtavouri N570. Both make top velocity, outstanding accuracy and have predictable performance over a wide temperature range. Fireforming loads also produce great accuracy and velocities around 3000FPS with 180 grain bullets, so even while forming cases the cartridge gives downrange performance roughly equal to the 7mm Remington Magnum.
Custom die sets are available through us, either Redding custom full length die sets or our in house die set built for use with Redding bushings/expanders. As this cartridge uses a .588″ case head diameter, we recommend building on an action sized for the .338 Lapua/.300 Norma cartridge families. AICS .338 CIP magazines work perfectly, with room to spare when it comes to overall length.