The 7LRM (Long Range Magnum) is a non-belted case that has the same overall length as the 7mm Rem Mag with a standard magnum case head. However, the body diameter is larger with no belt. The case neck is longer and the shoulder angle is 30 degrees. The case will fit and feed from a standard magazine box. Velocity with a 180 grain bullet is 3075 to 3100 fps from a 26-inch barrel length. See below for a comparison of different 7mm cases.
The brass dimensions and tolerances are outlined in Figure 2. Gunwerks has a very nice no-turn-neck, piloted reamer available to do custom barreling on your action—or start from scratch and have us build a full custom rifle. This is not a standard SAMMI cartridge; it is important to use a reamer with correct dimensions and clearances to ensure best accuracy, and longest brass life.
We needed to balance the requirement of a minimum-velocity threshold of 2000 fps at 1000 yards with a hunting weight bullet, and wind deflection numbers that will allow 30- 50% uncertainty in our wind estimation against recoil, cost, and case life for reloading. We wanted a cartridge of modern design that fit in a standard magazine box and would take any game we wanted to chase in all conditions— basically, the ultimate hunting cartridge.
First off, we settled on the 7mm diameter bullet because of the high ballistic coefficients of hunting-weight bullets from 160 to 180+ grains. Then we looked for a case to base the cartridge from, saving thousands in tooling costs. The 375 Ruger from Hornady was perfect. The 375 is very similar to the genius 30 Newton cartridge from 100 years ago. This cartridge case fits a standard magnum bolt face without modification, and there is no rebated rim as on the massive Ultra Magnum case. We fit the neck length to the longer 180 grain bullet, with the overall case length of 2.5 inches. With a 30-degree shoulder and minimum body taper, we achieve nearly 3100 fps velocity with a 180 grain bullet. If one compares the LRM case against two of our other favorite cartridges (the 6XC and 6.5-284 Norma) you will notice some striking similarity.
