The very best of your bolt provider groups. The best would be the regular 5.56mm bolt carrier team. Observe the bolt, cam pin and the carrier vital. On The underside is definitely the 9mm SMG bolt group. Recent generation is the AR6450 of Colt’s Law Enforcement Only line of weapons. https://remingtondscmu.answerblogs.com/26744350/an-unbiased-view-of-colt-10-5-inch-9mm-smg-upper-receiver-assembly