It depends on the brass make and how hot you run your loads. I have reloaded some 4 or 5 times in my .308 AR with mild loads and brass is still in good shape. I have shot some hot loads that give me only 1-2 reloads due to the primer pocket opening up. If you gun is running right, I can't see any reason for a difference in brass life between an AR and a bolt gun. Hot loads will trash brass. With gas guns, look for accuracy with mid-mild pressure loads. When you start running hot loads, it is harder on your rifle and brass.
