Originally Posted by BillM
The only AR style rifle I know of in the longer calibers are the Cobb MCR's,
and even then there are 4 platform sizes. http://securityarms.com/20010315/gal.../2900/2993.htm
There is a rifle out there that does 223 and 308 on one lower.
Colt LE901. Zero experience with it--just know it exists.
Wow, thanks! Yeah, I'm sure nowadays this lower may have gone the way of the Dodo, but just to know that one actually does exist somewhere is nice.
I think I'll probably just end up starting off with a standard AR-15 lower, finish off a really nice 5.56 variant, then head in the direction of an AR-10 for the power calibers. But I'll always keep my eyes peeled for the colt lower
Thanks a lot to everyone!