WayneinMaine,LR Turk rebarrel in .308
I have been picking up tools for a long time (9" south bend lathe, chamber reamers, receiver tap), and am about ready to launch a re-barreling of my large ring Turkish Mauser. I ordered a green mountain short-chambered barrel from Midway, as well as a receiver tap. The shank is .635, as best as I can measure with my plastic Lyman dial calipers. The shank of the old barrel is .525 so I have a gap at the shoulder of .110, about the length of the overhanging portion that secures the hand guard. (I wonder if the receiver was faced down to create the hand guard recess, since the dimensions should otherwise be the same?) At any rate, the solution seems to be to make a washer not unlike the recoil lug of a Remington or Savage, I'll probably have to thread it with my receiver tap because there isn't much of a shoulder on the barrel. I'm thinking of making it a thousandth or so thicker to account for some crush when tightened down. I haven't met a hardened barrel yet, would mild steel be fine for the washer? I have read in many places that torquing the barrel onto the receiver face only produces more accuracy than either just the torque shoulder or the torque shoulder and receiver face together. Does anyone have experience with this?
The length of the shank on the new barrel is .635”, the shank on the old barrel is .525”. If you decide to make a washer make it thinner, you want the face of the barrel to contact the seating/torque ring first, then there is crush, opinions are varied, crush and removing slack between the threads with smooth and straight surfaces could be .003”. I would cut the face of the barrel to shorten the shank which means your replacement barrel shank length would be .528”. Before torqueing the barrel to the receiver screw the barrel in until it bottoms out then with a feeler gage measure the gap between the face of the receiver and barrel shank shoulder.
Not something someone else would do: I cut the chamber first before I install the barrel , I measure the distance from the seating /torque ring down to the bolt face, I then measure case head protrusion from the face of the barrel, the difference in the two (+ or –) indicates the length of the chamber as in a short chamber or a long chamber, you do not want a long chamber unless you handy with a press, die and shell holder.
Finishing? The chamber can be left ‘a little short’ before installing then finished after the barrel is installed, I want to know how much case head protrusion there is between the receiver and barrel face, the Mauser? normally has .110” case head protrusion, again check the distance between the seating/torque ring and bolt face first. Not easy to grasp, the thing others call ‘HEAD SPACE’ is determined by case head protrusion, If I want clearance for reliable bolt closing I reamer the chamber an additional .005” more than the reading from the seating/torque ring, do not forget crush when torqueing, the case head protrusion will not change but the bolt face will move forward reducing the clearance fir bolt closing.
The length of the receiver ring was not the same on all Mausers, the 54-ATF was said to be compromised on strength because the front receiver ring was is shortened, to hold the top piece of wood. the nice thing about the 54 ATF rifles, they were large ring/large shank.
Cutting a barrel face, it must be straight. I secure the barrel on the gear end of the lathe with a collet. Along with what you have put together you need a dial indicator, with attachments, change that, you can not have enough dial indicators, and stands, lots of stands as in comparators.