AR15/M4 PMAG® 20 round .223 - MagpulProduct Details While the PMAG is optimized for Colt spec AR15 M4 platforms, modified internal and external geometry also permits operation with a range of additional weapons such as the HK 416 MR556A1 M27 IAR, British SA 80, FN SCAR MK 16 16S, and others. Similar to the MOE PMAG, the magazine features a long life USGI spec stainless steel spring for commonality, four way anti tilt follower and constant curve internal geometry for reliable feeding,