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#577591 - 08/12/20 10:39 AM Why don't shotguns ring chambers?
Shotgunjones Offline
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Registered: 02/16/03
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I have a black powder cartridge rifle in production. It's my first.

I'm studying loading both black powder and smokeless. My rifle will be a 45-70.

Cautions abound to not leave any air gap above the wad(s) with black, and to not use any wads with smokeless.

This is to avoid 'ringed' chambers. The mechanism most cited for this when it occurs is the bullet acting as an obstruction while air in the case is compressed to a very high pressure causing the ring.

The fellow who runs Shiloh Rifle has on his website a photo of a barrel sawed in half lengthwise that reveals TWO chamber rings, one where the base of a 405gr bullet would be, and one at the base of a 500gr. There is thus no doubt that this does occur.

Since the volume of air in the cushion section of a plastic shotgun wad is so large, the question I have is why does not a shotgun exhibit this phenomenon?
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#577594 - 08/12/20 11:16 AM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
Recoil Rob Offline
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Registered: 01/01/02
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Lower pressures?
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#577596 - 08/12/20 11:46 AM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
John Roberts Offline
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Registered: 03/21/02
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40,000 psi vs 10,000 psi.
JR
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#577598 - 08/12/20 12:08 PM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
craigd Offline
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If ringed chambers are ring bulges, maybe it can happen in shotguns? Maybe, plastic hulls can’t hang up like brass? It could be that it might not be so easy to replicate a rifle cartridge type void in a shot shell?

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#577600 - 08/12/20 12:43 PM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
Tim in PA Offline
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Registered: 08/07/07
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Two possibilities I can think of.

There is a lot of airspace in the wad, but the force required to collapse the legs in concert with the lower pressures involved, keep pressures from spiking.

The other is that the shot charge is easier to force down the bore so pressures don't get a chance to spike. When a 500 grain bullet hits the rifling, it's going to want to stop, spiking pressures.

Tim

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#577607 - 08/12/20 02:21 PM Re: Why don't shotguns ring chambers? [Re: Tim in PA]
John Roberts Offline
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Originally Posted By: Tim in PA
The other is that the shot charge is easier to force down the bore so pressures don't get a chance to spike. When a 500 grain bullet hits the rifling, it's going to want to stop, spiking pressures.

Tim


Agree.
JR
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#577636 - 08/13/20 02:05 AM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
Shotgunjones Offline
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I've considered all this.

The rings form where the base of the bullet is in the cartridge, so it would appear that rifling engagement has not yet occurred. In fact, there has been no bullet motion.

Inertia is inertia. An ounce is 437 grains, no matter if it's shot or ball.

True, shotguns do operate at lower pressures than rifles. These are black powder rifles though, and the difference isn't that huge. A trapdoor 45-70 load is in the area of 17K PSI for instance and a 3 1/2" 12 gauge is SAAMI specified at 14K PSI. They don't seem to ring chambers like rifles.

Kirk at Shiloh has stated that if you use the standard load of AA 5744 in a 45-70 case (which fills the case about 50%) and then top it with a wad in the mistaken belief that this is necessary to keep the powder in contact with the primer it will ring the chamber EVERY TIME. That has to be caused by a mammoth air pressure spike between the wad and the bullet and not the natural chamber pressure of the expanding powder gas. The load works fine with no wad. People use it regularly.

There's plenty of air in a shotgun shell between the over powder section of a plastic wad and the shot cup. There's a collapsing section between the two, but it sure does not seem substantial especially in the case of something like a Windjammer. 11,500 PSI in a standard load would seem enough to just smash that flat as if it wasn't even there.

What happens to the air? It can't go anywhere, just like the air trapped a in rifle cartridge that appears to compress and expand some really strong steel. I can't imagine what the actual pressure might be to actually do that. It must be enormous.

Obviously, this does not happen in a shotgun and shotgun chambers are generally not as thick and strong as rifle chambers.

I'm certain you're right about things happening more gradually in a shotgun, but this just boggles what little mind I have left.






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#577637 - 08/13/20 02:21 AM Re: Why don't shotguns ring chambers? [Re: craigd]
keith Offline
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I'm not so sure that the problem of ringing chambers in rifles has much to do with the difference in chamber pressures vs. shotguns, because each is designed to handle normal chamber pressure with a margin of safety built in.

Originally Posted By: craigd
It could be that it might not be so easy to replicate a rifle cartridge type void in a shot shell?


craigd makes a good point here, and a compressible plastic wad might replicate the function of fillers such as dacron in nitro for black rifle loads.

I'm using 13 grains of dacron with 4198 smokeless loads in my .450 Black powder express, with no sign of chamber ringing so far. But I have been strongly considering just switching to around 120 grains of 2Fg black powder because of warnings that it is only a matter of time before I ring the chambers.

I've wondered if it could happen because of not using enough dacron filler. It is a pain in the ass to stuff all that dacron in before seating the bullet, and I can imagine that some might want to use less than what is recommended. Yet it now occurs to me that I have also been shooting various published .45-70 loads of smokeless in my Marlin 1895 and other rifles without any filler whatsoever. And these loads are quite a bit higher chamber pressure than standard .45-70 SAAMI loads. There are many sources that say it is a must to use dacron or some other filler in double rifles when loading nitro for black, but nobody even mentions it when shooting cartridges like the .45-70 in Marlins, Siamese Mausers, Ruger no. 1's, etc. I do understand that there is a lot more air space in a 3 1/4" .450 BPE than in a .45-70 loaded to similar velocities. I suppose the chambers could be much thicker in these rifles than in typical double rifles. But this does raise some questions.
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#577638 - 08/13/20 02:36 AM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
Shotgunjones Offline
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Registered: 02/16/03
Posts: 3723
Loc: Michigan
I'm planning to start with AA 5744 in the 45-70.

Western Powders states to NOT use fillers or wads. They have me convinced.

They also make the claim that one reason AA 5744 works well in the old BP cases is because of it's low density but that would appear to be simply false. Looking at the Lee density table that comes with their volumetric powder measure 5744 has typical density for a stick type powder. A double charge would fit, and that would lead to disaster.
_________________________
"The price of good shotgunnery is constant practice" - Fred Kimble

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#577639 - 08/13/20 03:09 AM Re: Why don't shotguns ring chambers? [Re: Shotgunjones]
keith Offline
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Registered: 02/21/08
Posts: 10073
There is currently a discussion concerning the use of fillers in the Double Rifle forum. Not surprisingly, there are opposing views echoing what I have read elsewhere, and some interesting theories.

One guy says that chamber ringing is a gradual thing that may not be noticeable until it is too late, and case extraction becomes difficult. Another guy says that ringing will not occur with dacron, providing the correct amount is used.

And the recommendation from BrentD concerning the use of a small amount of flower arranging foam on a small smokeless powder charge sounds like a recipe for disaster, according to what Maj. Burrard had to say on the subject of chamber ringing. Not that I would even consider following any suggestions from BrentD on anything.
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