Pistol-caliber carbines are hot guns right now, but one limiting factor is that you'll need a dedicated lower receiver to feed either Colt- or Glock-pattern 9mm magazines. However, with the CMMG 9 ARC magazine, those who own a traditional AR-15 can also make use of the company's Radial Delayed Blowback upper receivers.

The CMMG 9 ARC conversion magazines feature the same external dimensions as a standard AR-15 magazine. The modified PMAG holds up to 30 rounds of 9mm ammunition and features a built-in feed ramp that takes up space in the magazine body.

Thanks to the design of the Radial Delayed Blowback upper receiver, this magazine also provides last-round bolt hold-open.