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Posted: 11/12/2015 5:40:26 PM EDT
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So I've built two mausers, one in 6.5x55 on a 95 action, and one in .270 WIN on a 98 action. The 98 is much worse about it than the 95, but both seem to throw shots after a few rounds. The 95 barrel is an Adams and Bennett that was install new and chamber reamed, the 98 barrel was used, but very clean and is within chamber go/no-go specs. The 95 will start throwing shots after about 5 rounds, but will then shoot well again after cooling. The 98 will center punch it's first shot, might be close on the second, and then can be any where after that.
Should I have used some kind of adhesive on the barrel threads when installing them? Both are free floated, any ideas on what might help the problem? |
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Sounds like either the barrels are not mated cleanly/square to the receiver, or the barrels are too thin, and starting to whip too much as they heat up instead.
When you mated the barrels to the receivers, did you square the face the the receiver, the inner contract ring, the receiver threads, the barrel shoulders to the treads/center line of the barrel bore, and you have the barrel breach face to receiver face the correct length? If you did not, then as the barrel shoulder metal starts to heat up and expands, it going to cause the barrel to cant off line instead? https://youtu.be/1Ufes_zrZmg If you are sure that the barrels where fully mated squarely to the receiver, the distance between the face of the receiver to inner seat was correct, and the barrels are not bent, then it could be that the barrels are just too thin to be free floated/over heating too quickly, and may have to single point bed them to stock instead. |
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You could experiment with bedding the tip of the forend, lightweight sporters often had contact close to the end of the wood to stabilize the thin barrel.
I would get some small post it notes and loosen the action screws, tear off a thickness to just fit under the barrel with the action loose, then tighten and check that the paper is wedged tight. Then go shoot and see if it helps. Temporary, as the barrel will settle into the paper and loosen soon, and paper is subject to moisture, but might tell you a direction. A permanent fix would be an epoxy pad under the barrel. No change and you're back to the barrel, or barrel receiver fit. Are you fitted to the c-ring or the front of the receiver? Did you square up or check the fit on the c-ring? I squared the c-ring and receiver, ended up with 80%+ contact on the c-ring showing on dykem, and a hairsbreath of daylight showing between the receiver and barrel shoulder on my 98 in 6.5x 55 AI. It shoots consistently sub moa, but it also has a big ass heavy barrel. 
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I believe I am fitted to the "C Ring". I understand sport barrels can be too lightweight and throw shots sooner than heavier barrels. In this case, the 6.5x55 is a very lightweight barrel, the .270 is almost a medium contour.
I will try the bedding suggestions with the forend of the stock. Both actions are glass bedded to the first two inches of barrel. If that doesn't work, I'll decide if I want to keep the rifles and have a gunsmith true the actions/shoulders, et cetera, or just sell and move on. Thanks for the suggestions, guys! |
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A temporary shim under the barrel near the end of the stock is a quick way to tell. You don't need a lot of upward pressure to see if this will work.
Did this on my 1909 Argentine Mauser in 35 Whelen and there was a noticeable improvement in the groups. Other thing to watch for is if the shots seem going back and forth between two groups you have a bedding issue with the receiver. |
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