I just got a 375 JDJ barrel (Thompson Center), and when I put in on my Encore frame, there is a gap of .006" Lock up is absolutely postively tight. The same gap exists with my 209 x 50 barrel Lock up is tight on it as well, and the barrel shoots like a house afire. It will stack Lee's 429-310-RF in Knight sabots pushed with 110 grians of Pyrodex on top of each other as long as I care to shoot, so the gap doesn't seem to resent any particular problem near as I can tell, just curious if it is within normal parameters of what you guys have seen.