no, springfield armories did that with the m1a awhile back- just a matter of sticking a 243 barrel on there- probably a different mainspring,( lighter) b/c of the lighter bullet weight, but it's a pretty minimal intrusion- when you go the other way- ie the 338 fed, i should imagine you run into the same problems as you do when you exceed 175s in the m14 platform- basically , heavier bullets beat the hell out of the action, oh yea, and a different front sight or a different ladder, as the 243 ballistics are different than the 308