Re: Changing AR upper receivers.
All lowers are not the same.A 308 upper needs an AR-10 lower.a 6.8 spc fits an AR-15 lower,as well as a .223 wssm,243 wssm,25wssm,30 Rem AR,450 Bushmaster,50 Beowulf, and probably a few more. The Ar-10 lower will accept a 308,243,and I dont know what else, I know there are probably others.
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