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Thread: Installing mauser military barrel

  1. #21
    Boolit Master
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    Well, this thread certainly went off on a tangent. The OP was asking about MAUSER re-barreling, not Savage. Different animal.....as the barrel attaching design is different....so NOT analogous. I don't know what torque is recommended for Savage barrel nuts...... but it hasn't got anything to do with Mausers, anyway.

    The "crush fit" technique, about which I spoke, involved machining the length dimension of the (threaded) barrel shank about 0.002" too short to allow the barrel face to contact the inner receiver ring, when the outer barrel shoulder made contact with the receiver face. Then, the barrel was over-torqued, to force the barrel face to make contact (essentially, stretching the barrel shank). This is the technique employed by most of the arsenals which made and assembled military Mausers. I can't fathom the reason for it, other than some misplaced notion that it produced a more "homogeneous" assembly, or would guarantee that the barrel would never "back out" under vibration. It certainly prevented barrels from "backing out"...... as judged by the incredible difficulty in getting most original military Mauser barrels off. However, it has NO value that I can see, because after decades of experience with Mausers.....I've NEVER seen one back out, anyway. The thread pitch is only around 5 degrees, which makes it VERY unlikely that a barrel will unscrew itself, if torqued to a reasonable value. Firing and handling simply don't produce enough vibration in the assembly, to cause this.

    Actually, 50 ft-lbs is fine.....but I don't recommend it, simply out of caution (you never know what actually number home gunsmiths will produce). Recommending 75 ft-lbs simply gives some assurance that at least 50 will be attained. But, I absolutely NEVER endorse the "crush fit" technique......it simply damages the threads.....and makes it far more difficult to remove the barrel later. And, as I said before, it does NOT provide any benefit. If one is worried about the barrel "backing out", for crying out loud, then simply apply a bit of NON-permanent loctite to the barrel threads.

    As regards cutting the barrel threads to a different pitch than the receiver....then forcing them together......well, perhaps some do it. I've never heard of anyone competent doing that, though. I consider that monumentally STUPID, however.....asking for trouble.....and I'd personally strangle the gunsmith that advocated that, if I still could. A bloody good way to ruin a barrel and receiver...and that's all, if you ask me.
    Last edited by bcp477; 12-06-2009 at 11:57 AM.

  2. #22
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    The Mauser Model 98 action has an inner shoulder called the "Primary Torque Shoulder." It is also called the "C Ring" and the "Inner Torque Shoulder." This is the surface that Mauser intended for barrels to be set against, but why? We know that Remington and most other modern manufacturers seat the barrel against the front of the receiver ring ("Secondary Torque Shoulder"). They don't even have an inner ring.

    The answer is in the geometry. I took measurements on a barrel that I had sitting on the bench. It is an Adams & Bennet F34 .30-06 barrel, and I figure that it is typical of sporter dimensions. I also measured a Czech 98/22 receiver. Here are the numbers:

    The actual contact area is 60% greater on the Primary Torque Shoulder. I actually cut the tenon about 0.002 inches long. That way when I draw up the action to the barrel, the Primary surfaces bottom hard (i.e., "crush fit"), and the barrel shoulder actually draws up to the feceiver face. That is not, however, necessary. It is really more cosmetic than functional.

    Now the above is all about sporter barrels. Military barrels are another kettle of fish. I measured a take-off barrel from a Yugo M48 Mauser. The shank diameter is 1.113 inches and the thread diameter is 1.102 inches. Those numbers would yield a contact area on the front (our A1) of 0.0191 square inches. That would make A2 14.4 times larger than A1. Obviously, seating on the front of the receiver is not even an option for a military barrel. Small ring Mauser barrels have threads that are 0.980 inches in diamter. Throw those numbers into the calculations, and the surface available on the front ring is 0.2186 square inches -- a lot more reasonable surface to deal with. The small ring barrels ARE seated against the front ring.

    For what it's worth..........

    Joe

  3. #23
    Boolit Master
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    "Small ring mausers torque up on the front of the reciever ring," from post number 15
    BUT I am a bit mistaken, forgot small ring 98's and the LR, .980x.775 long shank Turk which torque on the inner ring.
    As far as pre-fit barrels coming with 60*V threads that's the way its been as far back as I can remember(1978-79 ER SHAW) from most suppliers, probably just a ease of tooling thing. I do have a couple 55* lathe bits that I bought through Brownells(1993), but when I ground my own I chose 60* so I could fit it to my gage.
    As for wandering off topic, IT HAPPENS!
    Hell, I was there!

  4. #24
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    Quote Originally Posted by swheeler View Post
    I would think that if a barrel nut was the "secret" to accuracy, all those record setting benchrest rifles would be wearing one. On the other hand there are some custom BR actions with beveled locking lugs so that they can center themselves on lockup.
    ...and that's exactly not why AR15's and AR10's are so deadly accurate! Notice the barrel nut system in those.

    Joe

  5. #25
    Boolit Master
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    I know they can be very accurate, but it takes more than JUST the barrel nut. Heck just look at some of the groups shot by Mike in Co. Now I could be wrong, but don't think so, there are NO records held in National or International Benchrest Shooter Assoc by a "Black Rifle" in a sanctioned match.
    There are plenty of mausers out there with the barrel nut system for setting headspace and switching barrels, SMLE's too, but have never heard any claims to amazing accuracy improvement. Now I think we are wandering a bit far from amount of torque required on a M98 barrel swap and tools needed, GB asked about.
    Hell, I was there!

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check