The 50 BMG upper reciever is machined from a single billet of 4140 chrome-moly steel hardened to Rc 42-45 and Parkerized with a ... 50 BMG upper receiver for AR-15 lowers. The major difference is the action. JT Low Profile Adjustable Gas Block -. It includes a 15 1/4. Dismiss. fallout new vegas dynamic lighting rotherham council tax phone. Zel Custom Manufacturing introduces the Tactilite T2, a magazine-fed, bolt-action .50 BMG conversion for AR-15 style rifles. The T2 utilizes a side-mounted magazine design (similar to a Sten gun) on Zel Custom’s unique steel billet upper receiver. As a “firearms accessory”, the Tactilite T2 .50 BMG conversion kit requires no special.