Today I was a the range and fired off 30 rounds of Wolf Military Classic from an older magazine I had brought. After I reloaded this same magazine with 20 more rounds of ammo from the same case the rifle would not strip the top cartridge off the magazine and load into the chamber. Although I pulled the bolt all the way back to the stop it appeared like it was not grabbing the cartridge off the top of the magazine. Since I didn't bring my other magazines I wasn't able to determine the cause through process of elimination. Is this a common problem ? Is it likely the magazine or possibly the bolt not grabbing the cartridge when loading the first round ?