Reviews & Ratings for CMMG Mk4 4.6X30mm Banshee Upper Group Receiver — 1 review — Page 1

First 100 rounds of Hornady factory 38gr VMAX ammo resulted in (1) light primer strike, (3) failures to pick up the next round in the mag, and (10-12) failures to feed in which the polymer tip of the bullet was mangled as the round became stuck at an angle and would not enter the chamber. Three proprietary CMMG 40-rd magazines were used. With a standard carbine spring and carbine buffer, ejection was about 4:30-5:00 with and without a Dead Air Mask HD suppressor. Maybe Fiocchi JSP or FMJ ammo would be more reliable with the currently available mags. And maybe CMMG needs to improve their mags. For now, lots of money spent on an upper, mags, and ammo resulted in an unusable gun.