Colt 14.5″ XM4 prototype full heavy barrel with 1/7 twist.
This barrel was taken off an XM4 prototype upper for the early M4 program. The underneath of the barrel is stamped “X-26791-3″. It is test-fired only and has no throat erosion.
Features include: 1/7 full heavy barrel, A2 flashhider, sling swivel, handguard cap, front sight base with bayonet lug, A2 front sight post, barrel nut.
Markings: barrel stamped X-26791-3 on bottom side, front sight base C with M in bell