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Thread: Mauser Bolt Setback / Upset

  1. #1
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    Default Mauser Bolt Setback / Upset

    I just picked up a Browning Safari .375 H&H receiver and bolt that a friend had replaced due to being advised by a gunsmith that the bolt was "set back" or upset.

    I expected to see the bolt lugs peened back into the recesses in the receiver but what had actually happened was that the lugs on the bolt had been peened back around a .010 -.015" or so where they contacted the receiver. Remember this a .375 H&H length action so much of the bottom of the shoulder in the receiver for the bolt locking lug is removed to lengthen the action for the .375 cartridge.

    From this example it appears the weak link in reworking a 98 Mauser action is not the receiver but rather the bolt. I thinking just replacing the bolt body would get this action back up to shooting condition. The other option is to just rebarrel it with the proper headspace and keep on shooting it - the lugs should not have been waekened to any significant degree since the steel is relatively soft.

    Has anyone else the bolt lugs get upset or peened back in 98 mauser action? The pressures in a .375 are not any higher than any other magnm case so it could happen in any caliber.

    I should mention that the person that owned this rifle for several decades and hunted and shot it a LOT - probably much more that any of us would.
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
    ".. ask not what your country can do for you, ask what you can do for your country" JFK

  2. #2

    Default I have not heard

    of many properly manufactured Model 98 Mausers having this problem, unless excessive loads had been used frequently. Normally the 98 Mauser had excellent heat-treating, meaning that those parts which needed to be harder were and those areas that could be softer were done so. This is not a common occurrence. As far as the shoulder being in question, properly done, the surface areas where the bolt lugs contact the receiver should not have been diminished. I would question the headspacing.

  3. #3
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    Default Factory FN

    The whole rifle was a factory product sold by Browning and of course manufactured by FN - probably in the 60s. The bolt face is clean with only minimal errosion from primer leak-by so I don't think it was shot with excessive handloads. The .375 H&H is not normally a high pressure cartridge anyway - I would have been less surprised if it had been a Weatherby or Norma magnum.

    While the actual bearing surface for the bottom bolt lug was not reduced the supporting metal back of the lug seat is greatly reduced when the inside of the magazine area of the action or throat is cut-out for the .375 length cartridge. The metal is almost at a point on the top but in this case is still stronger than the bolt lugs. I wonder if FN hardened these actions as they are rumored to have done on the actions they supplied to Weatherby before the MK V.

    I'll continue to investigate this and post some pictures if I can get some close-ups. I may just replace the bolt body and go from there when I re-build it into another gun - perhaps back to the orginal .375 H&H.

    I'll also dig out a well used orginal Weatherby .270 Mag built on a FN supreme action and see how it looks. I picked it up years ago and have never shot it since it needs some stock repair - another project for a rainy day I need to finish.


    Quote Originally Posted by mauserboy View Post
    of many properly manufactured Model 98 Mausers having this problem, unless excessive loads had been used frequently. Normally the 98 Mauser had excellent heat-treating, meaning that those parts which needed to be harder were and those areas that could be softer were done so. This is not a common occurrence. As far as the shoulder being in question, properly done, the surface areas where the bolt lugs contact the receiver should not have been diminished. I would question the headspacing.
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
    ".. ask not what your country can do for you, ask what you can do for your country" JFK

  4. #4
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    Default

    If you know a local knife maker, perhaps he has a hardness tester. Mauser receivers were about Rc 38; not sure about bolts. It would be easy to test the hardness of both the bolt and receiver on your 270 and the damaged 375.

    I have experienced the reciever ring being set back but never the bolt lugs. I have seen the ejector slot on the bolt peaned closed enough that it would not open all the way but not what you are describing.

    I would be pretty careful if only because I have not encounterd this before. I would be interested in hearing how this works out for you. Good luck. J.

  5. #5
    hap
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    Default

    I have a commercial FN mauser action built into a 308Norma by my father in the late '50s, early '60s and used heavily. He was a pressure junkie...

    The bolt lug(s) on the ejector blade side developed deep creeks from the aft end of the split lugs in a long Vee and a portion calved off the thinner side. I replaced the bolt and lapped it in. The headspace is tight enough to make things a crush fit on brass fired with the old bolt, but just fine on new Norma brass. I think that means I had a little set-back and no clue...

    I find it telling the split side broke and the bolt from all appearances is the only casualty... I do rather like that extra Mauser lug...
    art

  6. #6
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    Default Softer bolt

    It would appear that your bolt is quite a bit harder than the one I have. Wish we could do a hardness test on both receivers and bolts.

    Most bolt and actions are hardened on the surface only with a softer core - some of the early guns had very hard bolts but that was in the early 1900s. I'm surprised a piece actually broke off the bolt - sounds like it was quite brittle for a modern bolt.

    I don't think the third lug really comes into play unless you have a massive failure of both the front lugs. The third lug apparently has a bit of clearance - on mine the third lug still wasn't contacting the receiver. It is indeed a nice safety feature and mauser did it right although it is tough to machine.

    I'll continue to research the issue - surely someone has tested the hardness of an assortment of these receivers and bolts. If I can find a shop with a tester I'll do it myself or pay to have it done.

    Quote Originally Posted by hap View Post
    I have a commercial FN mauser action built into a 308Norma by my father in the late '50s, early '60s and used heavily. He was a pressure junkie...

    The bolt lug(s) on the ejector blade side developed deep creeks from the aft end of the split lugs in a long Vee and a portion calved off the thinner side. I replaced the bolt and lapped it in. The headspace is tight enough to make things a crush fit on brass fired with the old bolt, but just fine on new Norma brass. I think that means I had a little set-back and no clue...

    I find it telling the split side broke and the bolt from all appearances is the only casualty... I do rather like that extra Mauser lug...
    art
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
    ".. ask not what your country can do for you, ask what you can do for your country" JFK

  7. #7
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    Default

    People load to stoopidly high pressures all the time; just read some posted loads on here.

    Have the received/recesses RC checked and if soft, have the thing re-heat treated. Cost you about a C-note.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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