If you were wanting to test a caliber, have a practice barrel, fire form brass or have a hunting rifle for you/the kids-- I have tons of barrels (roughly 50) of varying calibers. All have muzzle threads.
6.5 Creed (26"), 6GT, 6BRA (28"), 6 Dasher (28"), 25x47 (26"). Most of these are cerakoted...