I have a new barrel that will not headspace. It is a pre-fit. The go-gauge protrudes 0.130" from the barrel. That is in the range of other barrels I have for this action. It simply will not screw in enough to bottom on the gauge or come close (4 pieces of tape). Yes I removed the scope screws. Plenty of threads on the barrel. Barrel simply bottoms out before going in far enough. The only thing I can think of is that the threads are cut off perfectly square at the end of barrel. Most other of my barrels have a chamfer on the end.

What would be a simple way to add this? No lathe in my shop to do it with? Anybody got an idea other than a sander?

Yes the maker should fix it.... but you don't know the history of the barrel. Tiny