The large ring measures 1.45 on the front receiver ring, the small ring measures 1.35. These numbers are approximate because they are forgings not milled from a billet. The large ring has a barrel thread tenon of 1.100"x 12 t.p.i. , the small ring has a thread that is .980"x 12 t.p.i.. There are many variations when it comes to Mausers. Large ring w/ small thread, small w/large thread ect., ect. The '98 w/ large ring and thread is the one you want. All Mausers take extra work. They need to be drilled and tapped for scope mounts, an after market safety will be needed, bolt handle will need to be forged or cut off and another welded on. The front of the receiver ring should be "trued" but I'm not a fan of lapping lugs as these are 'case hardened' low carbon steel not alloy steel like modern actions. They make fine sporters or varminters when properly built. There are better choices for target/high precision rifles out there. I have several I built while I was in gunsmith school and a couple more on Mauser '98s' since then. They'll all do better than 1" groups @ 100 yds. w/ handloads. I'm particular about who made the '98 I'm planning on using. I'm partial to DWM, Oberndorfs', CZs', and those made by Steyr. The FN isn't bad either. You can do with the military trigger but you are better off replacing it w/ a good aftermarket one. That's alot of extra stuff to do verses a modern made action, especially if you can not do the work yourself.