I have an AR-15 that has a NATO spec chamber. I have access to a crap load of once fired brass .223 (not 5.56) winchester, remington, and federal. The brass was all fired from the Same full auto M-4. If I full length size this brass it should be good to go in my rifle right? I have hurd that you should not use brass fired in a SMG before but I dont know if thats true. I was wandering if its true if it is also true for a Machine gun.