Bought a heavily used 7mm mag. flatback/G series. in 7mm Mag. since then I got take off 270 Win and 30-06 barrels, and a fresh 7mm Mag barrel from Apache. All three feed fine from the blind, stagger feed magazine. In the case of a magnum round the lips may be relieved at the rear to accommodate the belt. gOOD LUCK WITH YOUR BUILD.