ok how about an ar15 bolt action upper thats chambered in 338 lapua or something other than a 50bmg. i think it would be feasible. not as big or heavy as a 50bmg and you get all the bust ass qualities of those guys sporting their accuracy int's saying AR's are pop guns. those smug bastards! I'LL SHOW YOU!!! I'LLL SHOW YOU ALLL!!!!........ sorry... as you can tell this is a somewhat sensitive subject for me.

It would be interesting, to say the least...

Cobb makes some interesting stuff. I believe they offer semi auto long action AR's in 30-06 to 338 Lapua. They also had a couple of bolt action 50's the last time I looked at their site.  

But not in semi auto though. Having a true bolt action upper thats been accurized, 338 lapua aside it should give the ar15 croud the option of comparing their uppers accuracy with that of their buddies customized rem700. at least you have it registered under one gun and you can switch with ease. Yet its not the modularity of the AR i have an issue with. its just the calibur choices and accuracy i want to address ya dig?

go to www.ferret50.com, they make what you are looking for. most of their uppers are in 50 bmg but on their price list they show them in 338.