Cross Machine Tool Co. AR-15/M16 BILLET UPPER RECEIVER, .458 SOCOM UPUR-3

Stripped billet upper drops onto standard lower and features expanded ejection port that accommodates .458 SOCOM and other big-bore AR-15 calibers. Integral Picatinny rail provides mounting space, and slick-side design does not require forward assist or ejection port cover, simplifying the build. Has M4 feed ramps, and accepts standard bolt carrier, charging handle and barrel nut, sold separately.