Re: Bushmaster Varminter .223, want .243 upper & barrel for deer any recommendations?
I'll second the 6.8 SPC. It will drop right on your .223 lower. I don't know about smaller towns but ammo can be had at places like Bass Pro Shops or Cabelas. I have a Rock River Arms upper on order for deer hunting right now. Figure on putting a red dot sight on it for still hunting and deer drives. Even out of a 16" barrel it has fairly impressive ballistics on the AR platform. The 6.5 Grendel is a proprietary round and really suffers when used with a short barrel. Unless you are talking long range shooting, it offers nothing that the 6.8 SPC doesn't. (I would like to have one with about a 22" barrel though, but kind of pricy.)
The 7.62x39 is certainly another option. Not quite as flat shooting but would be great on deer at moderate range.
The critters have to win every time, I only have to win once.
NRA Life Member