A little barrel work for a PR

[MD*GSP]

Hoping someone will look over my shoulder on this one and, perhaps tell me how to deal with a problem.

Awhile back I acquired a new-to-me 20ga P-Repro that I am liking quite a bit. The gun feels very lively and balanced in my hands beyond any other 20ga PR I’ve handled. I am fortunate enough to have a set of original PR 16ga barrels. With said barrels in place, the gun is just over-the-top nice and feels livelier still. Balance is just right. I didn’t get lucky enough that the 16ga barrels fit the gun to my satisfaction though (of course). Although I would have preferred to work the barrel hook to get the barrels fit to the frame just right, the ill-fit is in the opposite direction. With the barrels installed, the join of the barrel breech and the standing breech is off a bit. There’s a small gap at the lower portion so, theoretically (exaggerated of course), the muzzle is pointing up. Gun locks tight and the lever is about centered favoring the right. I could probably shoot it as is but, nah.

To fix it, I trimmed a pc of .002 steel shim stock but it wasn’t quite there yet so I trimmed a pc of .0015 shim stock to add to it. The action closed fine but the lever was a little far to the right and I could detect just a shade of mismatch at the top of the barrel join to the breech face. Went back to my cache of shim stock and carefully cut a pc of .003 steel shim stock. I cut it accurately so that it occupies the whole of the space between the water table. I also cut it long enough so that the entire bearing surface of the hook about its circumference maintains full contact. A little squeeze in a precision vise to flatten any curled edges followed by a wrap around a gage pin to get it curled proper before laying it in. Followed up with a dab of grease to hold it in place and, it lays atop the pin beautifully. The barrel join at the standing breech is now perfect. The barrel flats are lying perfectly along the water table and, there is a small gap at the ninety-degree flat / breech face junction. Perfect but for one thing. The rib extension (dolls head) stands proud atop the frame by about .015 - that’s alot. Although it’ll be fine for the upcoming season, I would like to final correct it so the barrels are perfectly fit beyond function.

How does one go about correcting the proud rib extension?

In the off-season I will find (or make) a roll joint that is .006 larger than the one that is installed in the gun as it sets now. That will eliminate the shim. Then I’ll refit the 20ga barrel set by cutting the hook back by .0015 on the Bridgeport and then creep into final fit by hand so it’s perfect and, tight.

To the experts, I'm not going to have to grind the barrel flats to get the rib extension flush top-side, am I?

Am I blinded and just not seeing another way to do it?

[MD*GSP]

Two pictures - 1 w/markup and 1 w/out.

I could work the surfaces down beginning at the frame and then taper (blend) the surfaces to the rib. Of course I'd have to re-engrave the small pattern but, that's okay.

[B. Dudley]

If fit is good everywhere else, then the only solution to the proud rib extension is to work it down to meet the frame and then re-cut the. Engraving on it. It is a common issue with meriden guns when fitting barrels up.

For the oversized joints, i offer them for sale, FYI.

[MD*GSP]

Thank you Brian. Having never been faced with this level of (irreversible) work on a set of barrels before, I haven't had to contemplate the options. Grinding the flats seemed a rather extreme necessity to me but I just couldn't figure a way to do it w/out wrecking the bluing etc. Of course grinding the flats assumes material exists to allow the mod in the first place. Then, there is the matter of identifying other elements of fit that would be affected and require attention. Thanks for setting me straight.

I really don't want to haphazardly go cobbling away at the barrel set. Thankfully they'll be usable with the gun come October. Therefore, using it as is for the upcoming season will allow for a level of certainty that the mod is warranted considering the irreversible nature of the required work. The set of 16ga barrels are not serialized to any gun, yet.

10-4 on the roll joint..glad you have some - it appears I may be in need of a rust blue come new year as well so..

[Mike Franzen]

Sounds like you have your work cut out for you. Where does one find those shims?

[Pa SxS]

I know very little about gunsmithing and nothing about metallurgy , but can't the dolls head be heated and bent down assuming there is clearence under the dolls head in the well?

Shims are easy to find and cheap on the internet.

[Dean Romig]

It's simpler and less intrusive Chuck, to simply file it to shape with the top of the breech and re-engrave the doll's head.





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[MD*GSP]

Originally Posted by Mike Franzen

Sounds like you have your work cut out for you. Where does one find those shims?

Yes, it’s a bit of work but it’ll be worth it. The intended gun feels unbelievably dynamic to me. My primary concern and, the reason I’m being extremely conservative in my approach is due to the irreversible work that is required to fit the barrels, as noted. The 16ga barrels, while not rare, are not that easy to come by. A set that has not been serialized is even more uncommon to find.

This barrel set fits two other 20ga’s I own, as is. Therefore, the decision to use the gun for the upcoming season before modification is a no-brainer considering I was able to achieve proper fit with a shim.

Here’s an order page full of shim stock from Manhattan Supply Co (MSC)

[Metal Shim Stock | MSCDirect.com](https://www.mscdirect.com/browse/tn/...vid=4287924361)

And here’s an order page from McMaster Carr

[McMaster-Carr](https://www.mcmaster.com/#shim-stock/=190imvs)

I prefer McMaster Carr but both outfits ship quickly.

If you page through the catalog pages from either supplier you’ll likely find small packages of shims with varying thickness instead of large-sized rolls of a single thickness that is tantamount to a lifetime supply.

[B. Dudley]

Originally Posted by Chuck Bishop

I know very little about gunsmithing and nothing about metallurgy , but can't the dolls head be heated and bent down assuming there is clearence under the dolls head in the well?

Shims are easy to find and cheap on the internet.

Not really. Then the front of the extension would have to be refitted. And besides, enough heat to allow any bending would melt the solder holding the extension on. If you want it bent, dropping it on the floor would be a better method.

[Bill Chadwick]

Let it be proud