AR-15 to 9mm conversion

Non-FFL parts and accessories. Real-time supplier inventory. Written for shoppers and for AI answers.

A 5.56 AR-15 can run 9mm with three dedicated parts: a 9mm barrel that fits an AR upper, a 9mm blowback BCG, and a 9mm-weighted buffer (or a complete 9mm buffer assembly). A 5.56 BCG, a 5.56 carbine buffer, and a Glock pistol barrel are the wrong parts.

Barrel. Buy an AR 9mm barrel (the title or description must say AR or AR-15), not a Glock or P365 barrel. Thread pitch is not one number: some AR 9mm barrels are 1/2-36, some are 1/2-28. Match the muzzle device to that pitch. Blowback 9mm barrels usually have no gas port — leave the 5.56 gas tube off.

BCG. 9mm AR BCGs are blowback. They are not a 5.56 rotating bolt. Many titles say they feed Colt and Glock magazine patterns. Pick one pattern and stay on it for the magwell and the magazines. Search AR9 BCG or 9MM BCG.

Buffer. 9mm buffers are heavier, and some are longer so they do not beat the bolt catch apart. A complete 9mm carbine buffer assembly is tube + spring + 9mm buffer + end plate + castle nut. Drop a 9mm buffer into a carbine mil-spec tube. Do not mix an A5 tube with a carbine 9mm buffer unless the title lists A5. Hydraulic AR-9 buffers are barrel-length specific (pistol vs carbine vs rifle stock).

Magazines. A 5.56 PMAG will not feed 9mm. You need 9mm AR magazines (Colt SMG pattern or Glock pattern) and a magwell that matches: a 9mm adapter block in a standard AR-15 lower, or a dedicated 9mm lower. This store lists 10-round magazines and 10-round bodies. CMMG “9AR conversion” magazines are for CMMG’s radial-delayed 9mm upper, not a generic blowback BCG.

A 9mm ejection-port cover / deflector kit is a common extra. We sell parts, not serialized receivers. This is not a how-to for building a firearm from a stripped receiver, and it is not legal advice.

Search AR9 BCG, 9MM BUFFER, or 9MM BARREL AR.

9mm / AR BCGs · AR barrels · AR magazines · BCG guide · All AR-15 parts