Hello, I'm new to the forum and hope someone can help me. I just purchased a new Bushmaster Preadator and I'm experiencing jamming issues when trying to shoot 556 through it. The lower is stamped 223/556 and will shoot 223 through it all day with no problem. However, when I try and shoot 556 it jams every time on the 2nd-3rd round. I have used PMC 55 grain JHP 223 up to 77 grain JHP 223 with no problem. The 556 I used was 55 grain American Eagle and Winchester FMJ and both jam. Any help/advice would be greatly appreciated. Thanks, Rob.