I have built ARs in 9mm, 45acp, .460 Rowland

.223, 6x45, .300 B/O, 358 Macho (before .350 Legend can about), 375 SOCOM, .458 SOCOM (AVOID Wilson Combat on either SOCOM).

.308 Winchester, .338 Federal, .358 Winchester, .375 Raptor and .458 Lott (yes, I said that right)...

It is VERY addictive.

HAVE FUN!

If you are not actively engaging EVERY enemy you encounter... you are allowing another to fight for you... and that is cowardice... plain and simple.