Below is a picture of my 90s era Diana 34. I wanted to know exactly why that wear on the top of the breech occurs? Going forth…what can I do to minimize that wear and could that be a culprit for lowered velocities?
What has happened to the breech of my air rifle
- Thread starter Arnie
- Start date
Terrible pic, can't see what the problem is.
If the metal of the breech is touching the metal of the receiver, that's a clearance issue and "shouldn't" be happening. Even without a breech seal fitted there should be clearance. You can either mill/file the breech to correct it, or weld/shim that ledge above the ball detent, but this could affect the lockup tension either negatively or positively. Depends on where you're at right now. The ball lockups are finicky at best.
If the metal of the breech is touching the metal of the receiver, that's a clearance issue and "shouldn't" be happening. Even without a breech seal fitted there should be clearance. You can either mill/file the breech to correct it, or weld/shim that ledge above the ball detent, but this could affect the lockup tension either negatively or positively. Depends on where you're at right now. The ball lockups are finicky at best.
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Looks like a clearance issue to me also. You could try putting a feeler gauge in there once it’s locked up to try to see what the differences are from top to bottom of the breech area.
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What you’re looking at here is the wear of the bluing on the top part where I’ve drawn an outline, and the bluing at the bottom has remained. Could I remove the ball lockup and install a wedge lockup?
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I just thought of something. What if I glue a washer in the place where the breech seal goes so that the breech seal is sticking out more? Or, would that wear the seal down faster?
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It is hard to see what you are looking at exactly from that picture. But I would agree with others, from what I think you are describing. When the barrel is locked/closed the tolerances between the breech and the receiver are not correct. Therefor you are seeing abnormal wear at the top of your breech. As to how and fix this.........I would refer to what thumper said.
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Sure the bluing loss isn’t from years of loading? If not put a few rows of plumbers tape or dental floss under the seal.
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The breech seal is not part of this equation. The breech seal shouldn't affect the lockup of the gun at all, it should be metal to metal. The ledge above the ball, against the wedge on the receiver. The breech seal gets slightly compressed to seal air. That's it.
Remove the seal altogether. Now close the gun and see what the issue is. If the breech touches the receiver, that's no good. It was a problem on some Diana's with the angled breech. If it's not severe, you can file the breech face a little till you have clearance. Probably only a couple thousandths at most will be needed. A good side benefit is your lockup will probably be better afterwards.
Pop a new breech seal in when you're done, and make sure it's not affecting the lockup when you're done.
Remove the seal altogether. Now close the gun and see what the issue is. If the breech touches the receiver, that's no good. It was a problem on some Diana's with the angled breech. If it's not severe, you can file the breech face a little till you have clearance. Probably only a couple thousandths at most will be needed. A good side benefit is your lockup will probably be better afterwards.
Pop a new breech seal in when you're done, and make sure it's not affecting the lockup when you're done.
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Yep, agree whole heartedly!! If you want it fixed right!! Then recrown that breech, no sharp edges wanted there!!
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It's a temporary fix but I have made thin shims to place behind the breech oring no glue for easy removal later when new oring is installed. There should be enough resistance on oring to keep it in place.
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If that air rifle has functioned good for 30 years, what changed. Certainly the metal between barrel block and receiver didn’t expand . The problem to look for is in the moving parts. Barrel pivot pin, holes in jaws, barrel block etc. Removing metal is a recipe for disaster.
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I agree that the breech seal protrusion doesn't have anything to do with your issue. The barrel pivot bolt does however. If the bolt has excessive wear it can effect how the barrel breech block fits into the receiver fork. Just a thought.
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The receiver fork holes don't see pivot bolt rotation. The hole in the barrel breech block does. The wear can occur there but I kind of doubt it. If concerned dial caliper it. The bolt itself could be the culprit. Dial caliper it as well or just eyeball it for wear. It does take much wear to create a problem.
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Despite others disagreeing I'll stick with what I said and did not say it was the absolute reason but a possible cause. You can easily & cheaply replace the breech seal, it won't hurt anything. You can also easily shim the top half of the breech seal (light fishing line as an example) and see if either of these things help. Simply get a black marker and touch up where the blueing is worn and see if there is any wear issues after. Otherwise if you have not noticed power, accuracy or lockup issues you could always leave it alone but keep an eye on things...
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