1. R

    AR10 - can 6.5CM and 308Win uppers use same lower (buffer/spring)?

    built an AR10 last year, and have 2 uppers - 308win and 6.5CM. probably only have a hundred rounds or so through each upper. 308win upper cycles pretty reliably, but more trouble with jamming on the 6.5CM upper. question - am I trying to do something that won't work (i.e. - common lower...