Ok chasing a little more advice - When cutting the barrel threads, the general consensus is to make the tenon the correct length so the inner C ring and outer leading edge contact their respective surfaces at the same time, maybe a thou or two one way depending on who you speak to. HOWEVER, these model Bs (as spud’s diagram shows) are like the military barrels in that their shoulder OD is essentially the same as the thread diameter. Meaning there is no shoulder to seat against. In general, the inner C ring isn’t 100% square (mine is 0.004” out cf the leading edge, which is 0.002” out). It seems unusual for people to lap the inner C ring, but not unheard of.

So, what is the standard for installing k98 or model B type barrels that have no shoulder? Do you lap the inner C ring to be 100% square? Do you not worry about 0.002”? Do I try and obtain (or make) a C ring lapping tool? Other option is I could get the shoulder say 0.050” - 0.100” wider to give it a shoulder - wouldn’t probably be overly noticeable. Then I could cut the tenon say 0.002” short and have most of the bearing surface on the (easily squared) leading edge)? I won’t be scoping this rifle, will the difference be noticeable? I doubt the inner rings wear, so I assume they wouldn’t have minded the 0.002” discrepancy at the oberndorf factory.