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Joined: Jan 2002
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basqulating?


birds are gone...dogs are gone...awl we got left are the gons...
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The French Ideal has a dynamic doll's head, with reciprocating wedges rising to engage the barrel extension. The shape is such that the joint is always tight, the parts wear in, keeping contact through the years. Most other doll's heads are kind of delicate affairs with static fit and no provision for wearing in.

The theory is that the doll's head resists the backward bending of the action on firing. Notice that no authority analyses what happens after the action has bent backwards. My guess is that if it does indeed bend, then it springs back to the original position with some force. It becomes a hammer, and so we must ask what is the "work" being hammered and what part becomes the anvil.

The traditionally held belief that the cartridge case pushes on the breech face by itself, and the barrels remain static, is a little suspect. My (unproven as yet) view is that barrel and cartridge become a single unit and both together push against the breech face. Indications that this is so are the imprints left by the barrels on the breech face.

If the barrel and cartridge push back together, then there is no need for any third bite. As people have noted on anothr thread, a double can be fired with no bolting in place, a sign that there are no forces acting to separate barrels from action during firing. And if this turns out to be correct then there is no role for any doll's head, not even the super tight fit one on the Ideal.

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A few thoughts on this theory. "IF" the gun is tight & on face & the barrels & cartridge come back together there should be no "Hammer" as the parts are already in full contact with the breech. "IF" on the other hand the breech springs away giving a gap & then springs back forward till it hits the barrel breeches this could account for the imprint on the breech face just as well as if the barrels hit it.
A good test of this theory is to remove the bolt from a Browning A-5 & fire it & see if the barrel & bolt recoil together as they do when locked. You can do the firing though, I'll Pass.
The other thread incidentally is referring only to the rotational portion of the forces & has nothing at all to do with this axial thrust.
"IF" everything worked as in your theory then you should never see a frame cracked at the bar & breech junction as there would be no force there.


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If you take a serious look at the dollshead on a Parker, you'll see it's of little value in terms of adding any strength. What it does provide is the guide slots for the individual ejectors and the stop for them. The crossection remaining after considering the slots and necked area, is very small.

As for the need for more locking strength, I beleive the forces trying to separate the barrels from the breach are relatively small.

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Well fitted dolls heads, side clips, hinge joints, cross bolts, under bolts, rotary bolts, under lugs, etc. all will contribute to a tight and long lived action, as does good action design. When these features are poorly done, the forces of firing begin the process of beating the gun to death starting with the first shot. Well made and well designed guns stand the test of time. Cheap guns quickly become rattletraps. The proof is in the parts boxes at every gun show. Although many more cheap Crescent and cheap Belgian doubles were sold at the turn of the last century, there are many more of the higher quality guns still in everyday use today.


A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.

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2-Piper,

The net is sprinkled with clips of people firing zip guns made with two sections of pipe and they hold OK. Richardson industries even offered such a gun which was basically two pipes fitting into each other with no bolting of any kind. You might be surprised as to how an A-5 would behave if fired unlocked. Provided the chamber is not highly polished I would be willing to fire one, you can watch from a safe distance.

Frame cracking occurs, I have photographed a few such accidents. The question is why the frame broke, because it was pushed back by the cartridge head alone? Has anyone ever figured out the Poisson effect and its contribution to the firing cycle of a shotgun barrel? The Poisson effect covers the radial expansion and axial contraction of thick walled cylinders under pressure. The breech end of shotguns falls within the definition of thick walled cylinders. Can such rapidly developing dimensional changes, even though small, affect a shotgun action? If so how?

How come some US made doubles with apparently weak lockups (L.C.SMith, Lefever) hold up over the years when triple bolted doubles shake loose?

These and other questions are puzzling. If some high speed photographers could film the action we will get an idea of what actually happens during the firing phase and the recovery from it. But most of them prefer filming more sensational shots of the shot exiting the muzzle.

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SGLover;
I realize there are many differences of opinion on a lot of things, but personally I do not consider the lock-up on either an L C Smith or the Lefever as "Weak". It is true that each has only one bolt, but that bolt is situated as far as possible from the hinge taking advantage of the extra leverage & quite obviously has proven to be entirely adequate on both. If you do a smoke test on the fit of guns with all those multiple bolts you might be surprised at just how many actually fit & thus provide anything at all useful to the bolting. This will be especially true om anything other than a very expensive & well fitted gun.
The vast majority of US made double rely on only a single bolt to hold the barrels closed. In the US many, many more guns were sold to "Commoners" than in the UK. The US makers "I Think" wisely concentrated on a single adequate bolt to keep the thing shut & did so with great success.
It is also noted that .22rf & many low intensity handgun cartridges in semi-auto form all operate on the "Blow-Back" principal, IE an unlocked bolt is blown back out of the chamber by the cartridges back thrust. As the cartridge's intensity increased it became necessary to go to a locked breech design. One old Spanish design by Astra did use a blow back design for the 9mm Largo & a few in 9mm Parabelum by the use of an extremely heavy bolt to slow down the back thrust simply by its inertia. This is also the principal by which the famous "Tommy Gun" operates chamber for the .45 ACP round. I "Very Seriously" doubt that an ordinary shotshell case has enough Grip on the chamber walls to make them a single unit as such.


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Dollsheads and sideclips bring to mind fender skirts and hood ornaments.

If looking for answers on how much axial force is exerted on the barrel, look at sleeving methods being used. Soldering and simple press fits.

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Interesting topic! I can only offer this.

All SKB, Miroku, Browning and most other modern production SxS use a double underlug, no extra bolting. Never have seen one get loose from shooting modern full pressure ammo. A few damaged by lack of cleaning/lubrication or stupidity. Merkel uses a cross bolt and the double underlug, the crossbolt is probably not needed. The most basic lock up of modern guns may be the Stevens/Savage 311 and variants. These guns get good mileage.

I would also like to see high speed pics of just exactly what happens when the gun is fired.

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2-piper,

Interesting point about blowback actions. But if you recall one of the problems in blowback actions was case sticking, and one of the ways invented to overcome it was the grooving of the chamber which allowed gases to surround the case and thus equalise external and internal pressures.

The blowback cycle starts once the inertia of the bolt has been overcome and by that time the bullet has left the barrel, pressures are at about zero. I suspect the same would happen in an Auto 5 without bolting if the chamber is not polished slick.

An interesting point about zipguns is that they keep together as long as the "barrel" mass is such that it does not overpower the frictional grip of the case on the "chamber" walls. When a heavy "barrel" is used then the "bolt" pipe does fly back smartly. This much is viewable on Youtube.

I am not advocating the manufacture or use of these abominations. But their behavior gives some interesting clues about what happens when a shotgun is fired.

American made shotguns are not weak, I did not mean to imply this, I did not express myself well in that post. On the contrary, they are plenty strong. However to the European conditioned shotgunner the single top bite seems weak. We Europeans assume that the only proper bolting for a SXS is via unerbolts, possibly aided by a top extension.

The simple practical top bite is not the only area where US makers pioneered new and possibly better ways to do things. The Lefever ball joint is a brilliant example of design foresight. It avoids all that messing about when it comes to tightening a loose shotgun. Amazing that it was not copied, but perhaps not, European makers tend to suffer from "mental inertia" as Gough Thomas pointed out.

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