Shotgunner,
I have a hvy barrel Bushmaster AR as well and have found a reload that it likes. Even though you mentioned wanting a heavyier bullet, you may want to try this. Its with a Nosler 50 gr BT, 25 gr of Benchmark, WSR, and LC brass. OAL is the max for the magizine. It usually does about 1/2" - 1" at 100 yds. Just a suggestion......
deerandduck