CO is right on with Mike, but you'll have to wait...he's super backed up now.

Quote Originally Posted by Colorado Osprey View Post
If you truely want a 45 cal in a performer, there is a gunsmith Mike Milli aka Dtech who excels and is a pioneer in off caliber AR-15's.
He will make you a WSSM necked up to .458 using rifle bullets instead of the .451-.452 pistol bullets of the Bushmaster.
Performance will be in excess of the 45-70. He also sells a .358 version to have less of a rainbow trajectory at longer ranges. Case capacity is performing to the 30-06 size case equivalent while still fitting in a AR-15 magazine. Olympic Arms did the initial research on the .458 version cartridge but never marketed it.
The 30 cal version is out performing the 30-06 and is just shy of the 300 Win Mag and makes the Black Out look like a BB gun.

His WSSM versions are available in .224,.243,.257,.264,.308, .338,.358 and .458 bores.

Mike is highly sought after and has a great following in the hunting AR community.