Maybe BCG,I think springs are same for .308 in LPK.Wolf has replacement springs for FN-FAL mags.Barrel nut is propriatary.Slash has buffer/spring assy.That's all I can think of brother Terry. <dontknow>
I think one of the advantages of buying upper/lower seperately is the 11% tax on a complete rifle.Although the price on the LAR-8 complete as apposed to just the upper that brother Jeff had as a link was not bad. <dontknow>