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Double Rifles, Single Shots & Combinations >> Building Double Rifles & Gunsmithing

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whitey
.275 member

Reged: 20/01/10
Posts: 83
Loc: Colorado, USA

O/U actions
#153554 - 13/02/10 04:49 PM

Another novice question. If the quality and gauge etc was the same. Which would be the strongest action.? The SXS or the O/U. Thanks Whitey Emwhanson@plainstel.comial

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4seventy
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Reged: 07/05/03
Posts: 2210
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Re: O/U actions [Re: whitey]
#153563 - 13/02/10 05:50 PM

If quality was equal for both, it would then depend on the design.

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whitey
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Reged: 20/01/10
Posts: 83
Loc: Colorado, USA

Re: O/U actions [Re: 4seventy]
#153602 - 14/02/10 02:27 AM

OK then if that is the case. As a novice looking at the two. As the receiver (action)
Seems to encase at least 1/2 but usually more than 1/2 of the total chamber area etc. Of both barrels. It looks like it should be stronger.??? Whitey

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baileybradshaw
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Reged: 21/06/08
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Re: O/U actions [Re: whitey]
#153732 - 15/02/10 04:53 AM

With break open guns, the issue is keeping the barrels on face. It's as much a matter of geometry as it is mass of metal. Break open guns try to open when firing due to the push back on the breech face and the barrels wanting to flip down from the bullet travel. Barrel wall thickess is enough to keep the side expansion in check, or the gun wouldn't last but a couple of shots. The pivot point on an O/U offers an advantage as it takes some of the leverage away from the barrels wanting to flip down, especially for the bottom barrel.

That being said, the hunge points for an O/U are just studs that don't span the width of the action. The walls want to flex away from the barrels, and since they aren't usually very thick, I can only speculate that is why you don't see O/Us in the really big calibers.

Throw in a third fastener, longer action bars ( reduces leverage on the hinge pin) and more support for the hunge..... I think the nod goes to the SXS.

Actually, my opinon of what would make the ultimate action for strength...a snap action ( side lever for my taste) trigger plate lock ( the lever cocks the hammers, the lockwork behind the action body so the bars remain solid) clamshell with Bissel rising third bite. That would take some serious punishment......hmmmmm

--------------------
www.bradshawgunandrifle.com

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whitey
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Reged: 20/01/10
Posts: 83
Loc: Colorado, USA

Re: O/U actions [Re: baileybradshaw]
#153746 - 15/02/10 06:36 AM

Bailey thanks I am learning something new. Whitey

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CptCurl
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Reged: 01/05/04
Posts: 5284
Loc: Fincastle, Botetourt County, V...

Re: O/U actions [Re: whitey]
#153776 - 15/02/10 11:17 AM

Quote:

That being said, the hunge points for an O/U are just studs that don't span the width of the action.

Not so for the vast majority of stacked double rifles. The Merkel and all German and Austrian O/U double rifles have a conventional hinge pin and various fasteners. The same is true of the Browning's and their knockoffs.

Here's a look at my Merkel 323E. You see the normal hinge pin. It also has Purdey bolts and Kirsten top fasteners. I would opine this is a pretty darn strong arrangement.

Curl

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YOUR DOUBLE RIFLE IS YOUR BEST FRIEND.

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whitey
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Reged: 20/01/10
Posts: 83
Loc: Colorado, USA

Re: O/U actions [Re: CptCurl]
#153784 - 15/02/10 11:58 AM

Cpt thank you very much for the pictures that helps a lot.And I can see you need all you can get with the big bores. PS that is one beautiful rifle. But my Social Security check and military retirement check won't spread that far. Smile Whitey

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Carpetsahib
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Reged: 29/04/07
Posts: 435
Loc: Western NC

Re: O/U actions [Re: baileybradshaw]
#153791 - 15/02/10 01:29 PM

Quote:

With break open guns, the issue is keeping the barrels on face. It's as much a matter of geometry as it is mass of metal. Break open guns try to open when firing due to the push back on the breech face and the barrels wanting to flip down from the bullet travel. Barrel wall thickess is enough to keep the side expansion in check, or the gun wouldn't last but a couple of shots. The pivot point on an O/U offers an advantage as it takes some of the leverage away from the barrels wanting to flip down, especially for the bottom barrel.

Forces required to keep the barrels on face is something that I have been interested in for some time. If one looks at the forces involved when a break-down gun is fired, the following are obvious: 1. Back thrust of the cartridge case upon the standing breech(+) 2. Forward thrust resulting from the projectile engaging rifling, and then friction whilst traveling down the barrel(+) 3. Friction of the case head upon the standing breech (-). (N.B.: The (+) symbols indicate a force that tends to open the gun. The (-) symbol indicates a force that tends to retard opening the gun.)

The pivot point is at the cross-pin, and that is usually offset from the bore axis; therefore there is a force-couple, in effect a rotational force, centered around the cross-pin. If the cross-pin was coincident with the bore axis, then the effective force-couple would be zero, and the action would tend to remain closed, even in the absence of a positive lock. That being said, the action of recoil against a pliant surface, i.e., the common human shoulder, would tend to break the joint and the gun would open in actual practice - if there were no positive lock.

Quote:

Actually, my opinon of what would make the ultimate action for strength...a snap action ( side lever for my taste) trigger plate lock ( the lever cocks the hammers, the lockwork behind the action body so the bars remain solid) clamshell with Bissel rising third bite. That would take some serious punishment......hmmmmm

I like your ideas; however, I wonder if the Bissel rising bite is any more effective than a properly fitted Greener cross-bolt. Is there more mechanical advantage with the Bissel due to the locking surface being somewhat further removed from the pivot point?

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baileybradshaw
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Reged: 21/06/08
Posts: 305
Loc: Diana, TX

Re: O/U actions [Re: Carpetsahib]
#153860 - 16/02/10 06:09 AM

Capt Curl,

I agree, that sure looks to be a hell for strong action. I wasn't aware of the full width hinge pins either. My only negative comment is the placement of that full pin is below the barrels, where there is more leverage against it, plus it is a short action. But with the double underbites, double Kirsten fasteners ( with the pins extending down from the bottom of the extensions) I doubt the action would ever shoot loose, and is probably as strong as any SXS. Thanks so much for the education.

I don't think the Bissel rising bite is anymore effective than a Greener or Kirsten bolting, but I like that it is more subtle. The greener is probably stronger as both sides of the crossbolt are supported. Plus, the greener will lock an action by itself, where the Bissel is intended to counteract the breech pulling away from the action.

I really enjoy discussions like this. So much to learn.....

--------------------
www.bradshawgunandrifle.com

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Carpetsahib
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Re: O/U actions [Re: baileybradshaw]
#154331 - 21/02/10 01:08 PM

Does anyone have figures for the forces required to push a bullet through a rifled tube? I have been making some calculations and would like to cross-check my work. I am assuming that the frictional force is directly proportional to the operating pressure. This seems reasonable, considering the tendency of a solid material to undergo transverse strain as well as axial strain upon the application of axial stress (Poisson ratio).

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doubleriflejack
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Reged: 11/11/07
Posts: 352
Loc: Oregon, U.S.A.

Re: O/U actions [Re: CptCurl]
#154942 - 27/02/10 10:01 AM

I have an Austrian made sidelock o/u, made in the 1930s, very similar to this Merkel, that locks up even today, tight as a rat trap, and in .270 Winchester caliber too, a very intense cartridge not generally considered suitable for a double rifle. I consider the Purdey underbolting with the German Kirsten bolting, such as this, to be one of the most excellent bolting systems ever designed, among the strongest ever designed. Though this bolting system was used on some German sxs rifles too, as well as these types of o/u rifles, I don't consider it worthy, as it makes for way too wide an action, ugly.

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