7X57 LR Mauser barrel (oversized thread)

[TCLouis]

I bought a new Milsurp barrel to put on a 98 action.

The threads are oversized and would only turn about 3/4 turn.

If my lathe had a thread Dial or reversible motor it would not be a big deal.

Anyway why were the threads cut oversize enough to prevent threading into an action?

[Gtek]

Do you have your old barrel? If old barrel is loose, go very slow. If you screw it in till one thread of shouldering and she is snug- no wobble, I would call that a good major OD. If she is fat on major visit your lathe, if not find someone who has thread cutter (and is good at it). The good ones always want the rec'r for fit, it is a feel thing. Option #2 if OD/ID good you can lap with compound with barrel vice and rec'r wrench. Many times together/apart/clean. Polish first two barrel threads-diss/clean, only put compound on threads 3 and 4/clean,5-6, you get the drift. Gtek

[Frank46]

I have heard about taking the major diameter down with files and working on the threads with silicon carbide paper on a triangular file. Frank

[leadman]

Brownell's does sell a tap for the large ring Mauser but it is pricey.

[Larry Gibson]

Brownell's also sells a die for much less. You can easily reduce the shank diameter (it is also recutting the threads deeper so the bottom of the cut fits also) with it. I have used it numerous times to fit barrels such as yours. You can borrow it but you might check Brownell's price as a new one may be cheaper than shipping mine both ways?

Larry Gibson

[zuke]

Chuck that barrel in your lathe and set it to it's slowest speed and put a triangular file into the thread about where it get's tight.
Do that a couple time's,try it and see what happen's.
If more need's to be taken off clean the file first and carry on till it fit's.

[303Guy]

Is it possible the old barrel was tightened up real tight to slightly damage the receiver threads? Maybe a little more tightening torque would turn in the new barrel all the way? The polish trick sounds good to me. I'm not a gunsmith but we are talking about threads here, not guns as such. A high pressure lube might be all that is needed to prevent galling.

[Frank46]

Never seize makes a good barrel thread lube to prevent galling of the threads. your local auto store should have it.
Frank

[Ray1946]

I have removed and fitted 4 Mauser barrels in the past. All of the barrels I removed were fitted very,very tight. Upon inspection of the threads in the reciever there appeared to be something like a shellac that was applied to the reciever threads before the barrel was installed. I used one of the stainless "tooth" brushes I bought at the gun show to remove this stuff. Remember; an action that is close to or more than a hundred years old might have issues other than just being "tight".

It seems to me that most old military actions were fitted to a crush fit. I would not remove any metal from the reciever, the best route is to very cautiously take as little metal as possible from the barrel threads, checking all the while for "fit" as you go along. It might take a while, but a good fit will create a much more accurate barrel...............................