[Unclenick]

OK. Ignore what I said about chamber draw. It's been a spell since I worked on a Mauser and I was thinking of the 96 Mauser instead of the 98. The 98 pattern Mausers have a second receiver ring down inside (the lower receiver ring) that is actually meant to be the primary torque shoulder, so you wind up crushing rather than stretching the barrel extension (the threaded part). I am guessing that is what is stopping your threading from going forward. Your barrel's extension is running into that lower receiver ring too soon. You can verify this by coating the back of the barrel with a Magic Marker and tightening it and then removing it and looking for the scuff marks.

The military barrels should have a 0.625" long barrel extension and if yours is longer (Kuhnhausen says you may see up to 0.650") that would explain what you are experiencing.

You will need to use a depth mic to measure the length from the front receiver ring (the front end of the receiver that the barrel shoulder meets) to that lower receiver ring, then compare it to the length of the barrel extension. You want the extension about 1-1.5 thousandths longer than the depth of the second ring surface.

The threads are actually 12 tpi Whitworth threads, which have a sharper 55° thread profile than the U.S. standard 60° profile. The wrinkle in this is that a lot of U.S.-made barrels have a 60° thread, so you wind up cleaning the original receiver threads up with a 1.100-12 tpi tap that has the U.S. thread profile.