If the barrel nut, barrel, and handguard are all standard, I wonder if Crusader would be willing to sell builder's kits to allow re-homing of parts from safe queen rifles or for a builder to make a new rifle in a custom calibre like 6 MM ARC, Grendel, or 7.62x39 mm? To confirm for a Comp set, a donor rifle could provide the barrel, gas tube, handguard, bolt, pistol grip, trigger and firing pin, while the kit would have to come with upper and lower receivers, trigger assembly area, bolt carrier / tail assembly, magazines and stock? An adjustable gas block may be needed to get the cycling right, since their is no buffer spring or weights to adjust. Would a builder's kits be useful?