Just dipping into this myself. Sent 2 barrels to Kampfeld custom to chamber up to my long action kelbly nanook. I know the Kelbly "can" accept prefits but I don't trust prefits. That's just me. I've heard just enough stories of issues and knowing my luck I won't go that way. I had him measure headspace himself so I can just send him barrels from now on. The two barrels now I'm getting this week are a 27 Sherman mag and a 33 nosler. Might take a but to get things changed but I can't afford a whole new setup everytime. There is something to be said for same trigger, stock, action, and scope in consistency.