https://www.cmmginc.com/shop/rifle-mkg-45-drb2-45-acp/ CMMG has a .45 ACP PCC with its radial delayed blowback mechanism. The delayed blowback reduces pressure before the bolt moves fully rearward, so they are able to use just a H buffer instead of the very heavy buffers typically needed for proper functioning of a pistol caliber AR. This should result in significantly reduced felt recoil. They also have built in a supposedly reliable LRBHO mechanism, which has been a challenge for Glock mag AR designs. If this works well, I'm sure they'll expand into 9mm since the AR-9 market is many times larger than the AR-45 market.