2011年12月6日 · usm4 yep , it isn't full auto though because you have to pull the trigger, it does a burst fire maybe 3 to 5 rounds with a pull of the trigger. ATF considers this legal and no ATF stamp is needed, check out the video. So for 900 on a lower receiver slap on you upper from a another ar-15 and you just about have a full auto weapon.

2014年1月22日 · USM4 Lowers. Jump to Latest 21 - 21 of 21 Posts. 1 2. C. craiga5144 · Registered. Joined Jan 15, 2014 ...