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Discussion Starter #1
I've been having a reoccurring issue in one of my PPK/S builds where the barrel apparently is rotating counter clockwise in the barrel hood.

At first I thought that perhaps my instilation of the barrel had not been precise when lining up the cuts on the barrel and barrel hood for the extractor to fit. Everything functions flawlessly until around the 40 round mark, when the weapon starts to get good and warm. I thought that as the metal started to warm and expand, it created a tightening environment which caused the extractor to snag on the barrel itslef.

This past range day however, I know it it's not the case. I reset the barrel absolutely perfectly and around the 40th round the extractor got caught once again on the barrell. The barrel had rotated counter clockwise 1mm or 2 within the barrel hood and was in the path of the extractor.

Does anyone who has done builds know a sure remedy for this. I want to keep the barrel if possible as it fits the West German build specs of the rebuild, is outstandingly accurate, and bluing is almost 100%.

Also possible causes? So far I'm thinking that whoever stripped the frame originally might not have done so with great care and may have stretched the barrell hood. Or perhaps the issue could be with the barrel itself or the barrell pin?
 

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My guess (having replaced barrels before in the PP series) is that the rotation of the rifling under firing friction is causing the barrel to rotate in that direction and finally being stopped by the cross pin. Plain physics. And there is play in the "should be a press fit" between the barrel & hood.
Remedy: Remove the barrel pin, tap out the barrel, since it is loose in the hood it should come out easily, mix & apply proper metal epoxy (JB Weld is good, but I like, Permatex Cold Weld better because it's thinner for tight places), apply on mating areas, rotate it quickly where you want the barrel after tapping the barrel back into place, wipe off excess epoxy and let it sit for 24 hours.
Then, drill out the 3mm pin hole with the next size larger (go SAE 1/8") and trim a 1/8" spring pin to size and tap that in.
Reason for the epoxy is to keep the barrel solid in the hood when drilling for a larger pin. If you don't want to use epoxy, you can raise some dimples on the barrel mating area with a sharp punch to keep it in place for the re-drill like one would do for a loose rear dovetail sight.
I don't like the dimpling procedure because the barrel hood on the frame is very thin and could lead to slitting & possibly spitting the thin hood. Epoxy is liquid and has more give to it.
Anyone else want to chime in if I forgot something?
Or, send it to M&M. He does excellent work.
 

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Some added thoughts:

Walther's fix --good for one time only-- is to knurl the barrel shank, then press it in. It needs to be a press fit. Before the cross pin is installed, if there is any wobble in the barrel-frame joint, you still have a problem. You'll then have to selectively fit another barrel, or
it may be that the frame boss is stretched too far oversize to be used --in which case it is scrap.

In any event I would be VERY reluctant to enlarge the crosspin hole in .380 gun. You are already extremely close to the inside wall of the bore, and after you drive in the pin, you're liable to find a speed-bump visible in the bore. If the cross-slot in the barrel is oversize, braze it up and re-drill to the original size.

Every attempt I've ever seen to secure a pistol barrel with epoxy or loctite eventually failed.

M
 

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Watcher never specified if his build is a .380, unless it was in another thread that I'm not going to look up.
My re-barrels were .22 & 7.65 mm. Same hood size/barrel shank dia in all three calibers. More beef in the .22 & 7.65 chamber/bore area for a slightly larger pin without the "speed bump" dilemma Mike stated for the .380. I see his point. The knurling solution is a really good idea. Worth the try, but what if the pin groove on the barrel has an curve to it? Won't it eventually rotate again eventually and rest on the stock pin in the 1-2mm rotation?
Hmm...let's help Watcher out on this if he wants to do it himself.
 

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Oh, and Mike, my epoxy idea was just to make sure the barrel wouldn't rotate when re-drilling for the pin. Not to be part of the barrel-to-hood securing. The pin is for that.
The knurling is about the same as my other suggestion of using a sharp punch to peen dimples. Same idea.
 

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Discussion Starter #7 (Edited)
The build was a .380. Interesting thing that I eluded to earlier was that the movement appears to occur when the gun gets hot. Once it cools the extractor fits in its place again. I haven't taken it out to the range twice in a row after the malfunction. I'd be curious to take it out once more and see if I can get another 40 rounds out of it before I tap out the barrel again. I have other barrels and I think I'll do a comparison the next time I remove it.

This was built solely for a plinking gun to make use of my accumulated spare parts. I prefer to shoot the PPK so if I can get 5 mags or so out of it per use, that will be sufficient for my needs.

I also want to try changing out the recoil spring. The one that I have is an extremely tight fit with one of those trimmed ends that slips under the barrel hood. Do you think that it is possible that it could be gripping and torquing the barrel as it compresses?
 
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