Bamafanforlife, The Turk 38 is similar in design to the 98, the barrel seats on the face of the barrel first then on the shoulder at the end of the threads, When measuring the receiver measure from the bolt face to to the barrel seating ring first then measure the distance from the front receiver ring down to the seating ring to verify the shoulder at the end of the threads will not contact first, the shoulder should not hit the front receiver ring before the barrels bottoms out.
Case head protrusion must be measured and compared with the distance from the barrel seating ring to the face of the bolt, this measurement does not vary more than .110 +or - a very few thousands.
I have two Turk 38s that are chambered in 8/06, I have two that will be 6.5X55 in time.
Torque ring? The barrel will bottom out when screwed in to the receiver, when the face of the barrels hits something that something is what some could call a torque ring, others call it the 'C' ring, it is a 'C' because it has a cut through the ring for the extractor, all other receivers are pope collars and or joints, the other barrels seat on the shoulder at the end of the threads, The Mauser has both the shoulder and 'C' ring, in the perfect world, the barrel face hits the 'C' ring first by as little as .003 thousands. I bottom out the barrel first then check the gap between the barrel shoulder front receiver ring with a feeler gage to make sure the shoulder does not hit first.
F. Guffey