COLT SMG UPPER NO FURTHER A MYSTERY

The upper is really a flat leading, naturally, and includes all the regular Mil-Spec fun things just like a dust deal with and ahead aid. It is actually a typical FSB and no I had no difficulties sighting it in. I originally crafted it which has a DPMS A2 upper receiver in advance of getting the 604 receiver. I'd no difficulties sighting it in Whi