CMMG Magazine Mk4/AR15 4.6X30mm 10 Round. 56mm AR15 magazines the patent pending CMMG 4.6x30mm magazine is designed to seat into a standard AR15-sized magwell in order to feed the CMMG FourSix upper receiver along with either a CMMG Mk4 or other AR15 lower group of your choice. Designed exclusively to feed the 4.6x30mm cartridge. Specifications for CMMG Mk4/ARr15 4.6X30mm 10RD Magazine: Manufacturer: CMMG Color: Black Magazine Capacity: 10 Round Caliber: 4.6x30 H&K Gun Make: CMMG Gun Model: CMMG Mk4 Gun Type: Rifle Quantity: 1 Package Contents: CMMG Mk4/ARr15 4.6X30mm 10RD Magazine What firearm models does the manufacturer say CMMG Mk4/ARr15 4.6X30mm 10RD Magazine is compatible with? The manufacturer says that CMMG Mk4/ARr15 4.6X30mm 10RD Magazine is compatible with CMMG Mk4CMMG 46AFC4D: Magazine Mk4/AR15 4.6X30mm 10 Round