A little barrel work for a PR

[Scot Cardillo]

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?

[Scot Cardillo]

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.

[Brian 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.

[Scot Cardillo]

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?

[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.

[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.





.

[Scot Cardillo]

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/Raw-Materials/Metal-Shim-Stock?searchterm=shim+stock&navid=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.

[Brian Dudley]

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

[Dean Romig]

Let it be proud

But that's not a finished barrel fitting. It wouldn't look right IMO.





.

[John Campbell]

It appears there are two ways to correct this fit.

1) re-contour the doll's head to flush and re-engrave/blue.
2) remove the rib, take metal off the bottom to achieve fit, then reattach the rib/blue.

Either way, it will cost money. The issue is how much he cares to spend. For a bit of proud metal.

[Scot Cardillo]

It appears there are two ways to correct this fit.

1) re-contour the doll's head to flush and re-engrave/blue.
2) remove the rib, take metal off the bottom to achieve fit, then reattach the rib/blue.

Either way, it will cost money. The issue is how much he cares to spend. For a bit of proud metal.

Nice. Good call - that hadn't even occurred to me. (work on the underside of the rib). Either that or, grinding the flats (assuming there's material) seems to be the proper way 'technically' because it maintains elevation poi in a manner consistent with the design. No way I'm removing the rib though. Besides, while I'm certainly not in a hurry to spend money, the notion of a one-off rust blue job doesn't sound horrible to me considering how gorgeous barrels turn out following such work. The 'technically' lower poi resulting from the blending of the dolls head frame>rib would be negligible, I would think..

[Tom Jay]

I too have a PR barrel issue and I'll start by asking this question; If the barrels lock up tight and also sit tight on face what's the purpose of the dolls head? Here's my issue; bought 0 gauge 16 gauge Krieghof barrels from a gentlemen on this Board to fit my 20 gauge PR. Took gun, original forend and barrels to Gunsmithing Ltd. to be fitted. In my own assemblage of the barrels to the frame the dolls head was about 1/16" or so short and not touching the back. I asked Mitch what could be done about the gap and he said it posed no risk to shoot and there would just be that little visual gap. I believe if I had asked (and paid to do it) he would have come up with a solution, but he thought it was no big deal so I have left it alone. Probably put a few hunded shells through it with no problem. Next spring I'll be looking for a Parker DH/E 20 gauge on an 0 frame and will most likely have the 16 gauge barrels fitted to this gun and will address the dolls head issue then. A few more questions, are PR dolls heads available from anyone? Thinking that if new are available in the white or blued the dimensions might be larger and could be made to fit. Does removing the screw on the dolls head remove it without screwing anything else up? Sorry but don't have a photo to post at this time...away from home on vacation. Thanks.

[Scot Cardillo]

I too have a PR barrel issue and I'll start by asking this question; If the barrels lock up tight and also sit tight on face what's the purpose of the dolls head? Here's my issue; bought 0 gauge 16 gauge Krieghof barrels from a gentlemen on this Board to fit my 20 gauge PR. Took gun, original forend and barrels to Gunsmithing Ltd. to be fitted. In my own assemblage of the barrels to the frame the dolls head was about 1/16" or so short and not touching the back. I asked Mitch what could be done about the gap and he said it posed no risk to shoot and there would just be that little visual gap. I believe if I had asked (and paid to do it) he would have come up with a solution, but he thought it was no big deal so I have left it alone. Probably put a few hunded shells through it with no problem. Next spring I'll be looking for a Parker DH/E 20 gauge on an 0 frame and will most likely have the 16 gauge barrels fitted to this gun and will address the dolls head issue then. A few more questions, are PR dolls heads available from anyone? Thinking that if new are available in the white or blued the dimensions might be larger and could be made to fit. Does removing the screw on the dolls head remove it without screwing anything else up? Sorry but don't have a photo to post at this time...away from home on vacation. Thanks.

Tom, it's the front edge of the dolls head providing the functional lock of the barrel to the standing breech. By design it literally intends to hold the barrel tight up against the breech instead of separating under load and, relying solely on the under-bolt. Your gun is safe. ‘Theoretically’ your dolls head is not as robust compared to a dolls head that fully occupies the pocket machined in the frame simply because there’s less material but, it will not fail. The aesthetic would bother me. A good gunsmith with welding skill could likely build material so that the space can be eliminated but that would also require some extra work contending with the dovetailed plate that stops your ejectors. Adding material to the pocket in the frame would be a mistake in my view. A savvy gunsmith could make a new dovetailed plate that would occupy the space without having to weld any material at all ‘if’ there is enough of a gap there to allow a degree of material to work with (kind of a catch 22). And, of course, if you were willing to pay the hrs it would take to complete the tedious task - trust me, gunsmiths are underpaid. The radii x2 at the rear of the extension would be tricky to blend in order to make the repair invisible - engraving would help to hide imperfection if deliberately executed by a good eye.

Maybe someone else will chime in and tell you that it's far less complicated..I dunno', I've never done it and there are plenty that have. It's a shame you have a gap there.

[Dean Romig]

The 'doll's head' provides no function at all. On an ejector gun only does it serve a function - that being a housing for the ejectors to slide in and to facilitate a mount for the ejector stop plate.

Competition shooters of old sometimes ordered their Parkers without the doll's head rib extension and it was eliminated from the Trojans around 1920 or so.
In fact, all Parkers were made without the doll's head rib extension until sometime in the early to mid-1880's.





.

[Scot Cardillo]

While I agree that the dolls head is marginally functional considering one could cut it off and shoot safely, what do you make of the Greener cross-bolt Dean?

[Dean Romig]

I know nothing about the Greener cross-bolt system. My focus is almost entirely on Parker shotguns... that is enough for me and pretty time-consuming in itself.






.

[John Campbell]

Ask any classically trained double gunsmith and he will tell you that these doll's heads, Greener cross bolts, Scott bolts, etc., exist primarily for psychological reasons. Virtually none of them are fit up to engage surfaces for locking.

In plain language, they were fashion-of-the-era sales gimmicks. And as Dean points out through the Parker Trojan example, generally unnecessary.

The one exception I can think of offhand is the original Westley Richards A&D box lock doll's head. It engaged a sliding top bolt to lock the gun... not the frame. Later, the Purdey double underbolt was added, which made the top bolt superfluous .

[Scot Cardillo]

I appreciate the input gentlemen and believe me, I have great respect for your knowledge - somehow I feel like I might be opening up a can of wa on myself..lol. I sincerely just want to understand because I’m not seeing it. I have to wrap up a few things so I'll have to come back to this thread. I hope you gentlemen are willing to take me to school on this one.

Here goes..

Sorry but, the classically trained double-smiths are just flat wrong..lol :duck:

[Scot Cardillo]

Please forgive the lengthy (and at times elementary) post - likely full of typos and rambling. I have to admit that I’ve not looked at assembly drawings beyond part id so maybe I’m way out of line or totally off base. I am also no gunsmith nor do I claim to be. That is to say - this is only what my mind’s eye shows when I think of how a box lock works. I would greatly appreciate further understanding through correction from those that know.

To anyone kind enough to read this through step by step, where am I mistaken?

—

Ignoring gravity. Lay a loaded barrel on a flat and the barrel face back against a vertical surface (breech) so that all gasses are contained and do not escape out the rear when a cartridge is fired. No lock or hinge engagement at all.

Pull the trigger - the action (frame) propels rearward and the barrels propel forward. The surfaces separate. (barrel face and breech) Velocity of the cartridge (as intended) is low because gas escapes.

Add a hinge - pull the trigger. Action propels rearward and barrel movement forward is disrupted by the hinge. The energy is now violent because of the hinge’s sudden disruption of barrel motion and compounded further by the spike in velocity due to the partial containment of gas. The energy has nowhere to go so it’s directed upward toward the path of least resistance. The barrel separates at the top of the breech while the base of the barrel remains tight at the breech base. The barrel folds downward about the fulcrum created by the hinge.

Add the under-bolt - pull the trigger. The bolt controls upward barrel movement therefore, preventing the barrels from folding, to an extent. The stack-up of tolerance between the bolt and the bolts channel in the frame equals the distance that the barrels will move upward under load. When this occurs, the barrel will separate from the breech at the top but remain closed at the bottom due to the hinge that is preventing forward movement. (the fulcrum). Velocity skyrockets.

As the bolt and bolt channel begin to wear, the stack-up of tolerances begins to open up as clearance between mating parts increases. Therefore, upward movement also increases, allowing for higher separation between barrel and breech at the top while the bottom joint remains tight. (assuming hinge and barrel hook has not worn)

The dolls-head barrel extension intends to hold the barrel up against the breech in a straight line in unison with the hinge under load. Therefore, containing all energies and forcing them in one direction, backward, while at the same time preserving all gas for cartridge velocity. The barrel and action are now one pc because the breech is captured by the barrels at the extension up top, the bolt at the bottom, and the hinge pin.

As I understand, this helped but it was flawed because it didn’t fully account for the store of energy channeled to the hinge creating a fulcrum which would still send energy upward. Hence, the cross-bolt. This combination of locks, now contains ALL of the energy so it is now directed rearward under load. The stack-up of tolerances becomes a virtual non-issue because geometry of the various locks lends itself to containment of all movement, inherently. Barrel separation at the top of the breech under load becomes virtually non-existent. Further, the cross-bolt now limits the heavy lifting required by the underbolt because when clearances max out, the cross-bolt limits further upward movement which substantially reduces strain against the underbolt and, the barrel lug for that matter. This relieves the brunt of energy that the underbolt would otherwise have to handle if the cross-bolt wasn’t there to limit travel. The underbolt will eventually wear, maybe, but it will only wear from friction. The cross-bolt also benefits the underbolts channel in the frame by offering protection of the no-tolerance fit that the machinist worked carefully to achieve while building the action. The protection of the no-tolerance fit also inherently offers a great deal of protection to the frame itself which is case-hardened so that it resists frictional wear between bolt and channel, yet the core of the frames material remains ductile instead of being inherently brittle and prone to fracture as a result of, strain.

Some manufacturers dropped the cross bolt and incorporated a bite at the top lever thinking it more efficient.

Parker did something different. Parkers approach was very clever, dare I say superior to the cross bolt as it relates to longevity of the entire mechanism despite potentially higher maintenance requirements.

Dean says otherwise (and my reverence for his knowledge would not allow me to dispute his assertion). However, from a mechanical viewpoint, assuming Parker incorporated the extension into their design for strength and function (i.e., ejector guides / stop plate).

Parker added the removable wedge. That’s genius in its simplicity because that wedge is designed to wear and it’s a sacrificial item. I can only guess that it is intended to be softer (lesser heat treat) than the underbolt that engages it. As the wedge wears, the user will notice that the lever is approaching center. It’s common knowledge that once the lever approaches left, the gun needs attention. What also happens though is the front face of the barrel extension will begin to wear as movement of the works increases under load. If the wedge is replaced before movement under load increases, the only wear to the extensions bearing surface will occur as the action is opened and closed by the guns owner. That wedge assures protection of the extensions bearing surface and negates the necessity of a cross-bolt. The owner also gets the benefit of longevity of the guns inner works because all movement under load is controlled at all times. Movement in a mechanism that is not controlled allows for rapid wear because wear is not linear once it begins. At any time, the wedge can be replaced and voila -a tight gun. Great design.

John Browning - John Browning saw something different. John Browning removed the hinge and captured the energy. Pure_ genius.

All that said, the well-established expertise that the double-smiths who determined that the extension or bolt, unnecessary; I would guess, totally correct however that does not negate the engineering principal that is totally correct. Or, I’m missing something altogether.
Thank you, John for sharing your wisdom. Also, thank you Dean for pointing it out as a practical matter.

Please feel free to comment.

[John Dallas]

I think a possible flaw in your thinking is that I don't believe the barrels are "propelled forward". The breech would go backwards, resulting in a separation (assuming the actions is not constrained by your shoulder as an example), but I don't understand what would propel the barrels forward.

[Scot Cardillo]

Wouldn't the force of the breech going backward also push the barrel forward? Maybe not one to one, but forward nonetheless?

[John Dallas]

Not in the physics classes I took, but that was 50 years ago, and things may have changed

[Scot Cardillo]

lol..touche'. So if you mounted a gun up to your shoulder as a back-stop, the barrel would remain stationary (figuratively speaking) as your shoulder stops rearward movement of the frame once the gun is fired? Don't misunderstand, I'm not suggesting that the cartridge carries the barrel like a projectile, of course.

[John Dallas]

I suppose that after the breech separates from the barrels as it moves rearward, that the escaping gases going out between the breech and the barrels could exert some very small forward pressure on the barrels, but i would judge that to be minimal

[Dean Romig]

Physics says that "for every action there is an equal and opposite reaction."


I would also add that the angle between the breech face and the action flats (water table) is ever so slightly more acute than a perfect 90 degrees. This would change a lot of people's thinking of an upward force upon discharge.





.

[Scot Cardillo]

Physics says that "for every action there is an equal and opposite reaction."


I would also add that the angle between the breech face and the action flats (water table) is ever so slightly more acute than a perfect 90 degrees. This would change a lot of people's thinking of an upward force upon discharge.





.

Exactly correct.

I did a poor job of laying out the fact that my logic intends a definite stop of rearward movement as the barrels are being carried (by the hinge) backward. Once it hits stop, force reverses direction and that action gives rise to an equal, reaction (forward barrel motion as the frame remains in a fixed position 10lbs rearward>stop>10lbs forward) I wasn't 100% certain of the exact 1 to 1 reaction though b/c of gasses

The standing breech not at ninety-degrees is something I hadn't even considered.

[Scot Cardillo]

Physics says that "for every action there is an equal and opposite reaction."


I would also add that the angle between the breech face and the action flats (water table) is ever so slightly more acute than a perfect 90 degrees. This would change a lot of people's thinking of an upward force upon discharge.





.

Just had a look - thank you Dean :bowdown:

How in the world did I miss that - 'tis why I'm willing to put myself out there and look like a j-ass.

The classically trained double gunsmiths have it right and I am just flat wrong :duck:

[Brian Dudley]

Back to the idea of dropping the barrels down by "grinding the flats". This will simply
Not work because then you are moving the center point of the barrels down which, if done enough, can cause the firing pins to not contact the primers correctly resulting in misfires.

This whole subject is simply the the matter of all of these guns being individually hand fitted and the amount of variattion that exists from gun to gun. It is simply the nature of the beast that sometimes can be reasonably worked through and somtimes not.

[Scot Cardillo]

Thanks Brian - good point. I did consider that and you are clearly right. In my case it wouldn't shift enough to be problematic but that would have to be considered on a case x case basis. I wouldn't want to go more than about .02 off center, personally. The area I would want to study closely and understand clearly before adjusting flats would be the fore iron.

I have to say, I'm really glad that Tom asked his question because I got the chance to learn that I don't know what it is I think I know about double gun design. I've got some studying to do before so much as putting a file to any working surface. The barrel face is nested in the breech face - that sends forces somewhere, and it's not how I visualized it, at all. Heck, I'm feeling uneasy about a simple shim at this point. I can gather and cipher some numbers and all but, can anyone point me to some legitimate working / manufacturing drawings of a box-lock action? Reference materials that will short-circuit the learning curve?

[allen newell]

I had Brad Bachelder fit up a set of Parker Repro barrels Q1/Q2 to a GHE and we decided that as long as the face of the breech was tight to the frame we'd just forgo working down the top of the breech balls and re-engraving the top rib. I shoot it and while it's a a little proud, I do well on skeet with it and look forward to taking it to northern Maine this season on grouse and woodcock. Maybe sometime down the road when I have some extra cash on hand I'll have Brad finish it off. My advice is as long as it's tight to the frame and it doesn't bother you too much, let it be for now and just shoot it.