Barrels are standard AR15 pattern, but with an enlarged Gas Port. The Gas Port, mated with the standard, adjustable Gas Block will ensure reliable feeding with all brands of ammo and bullet weights, to include compatible calibre changes.
Being standard AR pattern barrels, rebarrelling for the purposes of a calibre change will be a simple do-it-yourself matter of unscrewing the 4 bolts securing the Barrel Nut and swapping over the Rifĺe-length Gas System. Barrel changes for the purpose of installing a shorter barrel may be problematic in terms of finding a compatible Carbine-length Gas System. My testing will not cover such a conversion, which is best left to the tinkerers to attempt.