20 gauge chamber length

[Scott Chapman]

The google document that I posted was previously posted by Drew Hause back in April of this year. He wrote:

"Major Sir Gerald Burrard, The Modern Shotgun, Volume II, “The Cartridge”, 1955 3rd Revised Edition, p. 154 in reference to modern “star” crimped paper cases
“For all practical purposes any increase in pressure due to the longer cartridge case really does not exist provided the correct powder and shot charges for a nominal 2 1/2 inch cartridge are used.”

Obviously this applies to 2 3/4" hulls in 2 5/8" 12g chambers.

A summary of Bell's and Armbrust's study “Long Shells in Short Chambers”, in “Finding Out for Myself” Part V, Double Gun Journal, Winter 2001 is about 1/3 down here
https://docs.google.com/document/d/1...vwLYc-kGA/edit

The pressure increase for one load was 1200 psi

OTOH: I had a 1924 20g Parker with chambers slightly longer than 2 3/8". Recoil with standard 2 3/4" 7/8 oz. skeet loads was severe, and the case mouths were feathered, evidence that the hull had entered the forcing cone."
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[Bill Murphy]

The long and the short of it is that these are shotguns, fired at low pressures, from thick barrels. It just doesn't matter how long the shells or the chambers are, as long as the shells are not overloaded, everything will be fine, the pheasants will be dead and the guns will not blow up. I think Dr. Drew and others have clarified that in past research.

[Drew Hause]

Scott: please help us understand your question.

Scroll down about 1/3 here and there are several references to shell and chamber length
https://docs.google.com/document/d/1...vwLYc-kGA/edit

“Mr. Griffith on Shotgun Patterns”, 1897
https://books.google.com/books?id=inQCAAAAYAAJ&pg=PA234
Studied “Turnover” – case longer than the chamber in reference to vintage roll-crimped shells

Charles Askins “The Cone” Field & Stream, Nov. 1921
https://books.google.com/books?id=UP...J&pg=PA700&lpg
W.A. King for Parker Bros.
Referring to the cone, we ordinarily permit our shells to lap into it 1/8-inch, but as a matter of fact we have found that the majority of guns will shoot a better pattern with even more lap than this. In fact, we can secure extra good patterns by shooting extra long shells, permitting the lap to extent to the point where we begin to tear off the ends of the paper. At that point we do not seek to give more lap. In user’s hands we do not advocate the use of longer shells than those which give 1/8 lap.

Everything in the shotshell world changed when Remington introduced the ‘SP’ high density polyethylene compression formed hull with a separate base wad in 1960, followed by the polyethylene ‘Power Piston’ wad in 1966.
Winchester/Western introduced the Mark 5 polyethylene shot collar in 1961, followed by the one piece compression formed plastic hull for the Super-X in 1964 and AA Target shells in 1965.
The Federal Riefenhauser (straight wall) ribbed plastic shotshell was introduced in 1965.

Many modern 2 3/4" plastic hulls are indeed a bit shorter than 2 3/4" after firing; the box is still labeled 2 3/4".



I think there are good reasons to not use 2 3/4" loads in a 20g with 2 3/8" chambers.
2 3/4" 12 g loads are of no concern in 2 5/8" chambers.

[Scott Chapman]

Dr. Drew: I didn't have a question. Dean asked me for the author of the google document. I had reposted your info from a April 2019 thread in order to provide insight as to the variations in length of fired modern 20 gauge plastic shotshells.

From my keeping up with the discussion on this forum and additional reading, it is my understanding that many learned students of turn of the century fine shotguns believe that 20 gauge guns with 2 3/8" chamber were made to shoot 2 1/2" shells and 2 5/8" chamber guns were made to shoot 2 3/4". However there is variation in the length modern plastic shotshells which can muddy the waters.

Some on this board report to regularly use 2 3/4" shells in guns that are not 2 5/8" chambered, while some will only use 2 1/2". Some argue that it is more about the pressures generated (specifically when talking about composite barrel) and the stress on the old wood.

My take home message is that the more valuable a gun is and perhaps the older (composite barrels +/- oil soaked wood) the more likely the owner is to shoot low pressure RST 2 1/2" shells. I feel that you can't go wrong with this option even with a shooter quality VH or Trojan.

There are some that use standard 2 3/4" ammo in fluid steel barrelled guns (with adequate wall thickness) and never look back. Including heavy pressure waterfowl loads.

It is all what you are comfortable with personally. If you are worried about whether a 2 3/4" shell is going to pattern poorly, produce too much recoil, etc. etc, go out and shoot it on a pattern board and find out. If you don't want to go to the trouble, spend a little extra and buy RST shells and don't worry about anything!

[Ken Hill]

Another interesting thread on 20 gauge chamber length f I'm 2017. http://parkerguns.org/forums/showthr...&highlight=RST

Also, the last time someone asked RST the 2 3/4" loads were lower pressure than their 2 1/2" loads. http://parkerguns.org/forums/showthr...light=20+gauge

Ken

[Bruce Day]

Originally Posted by Bill Murphy

The long and the short of it is that these are shotguns, fired at low pressures, from thick barrels. It just doesn't matter how long the shells or the chambers are, as long as the shells are not overloaded, everything will be fine, the pheasants will be dead and the guns will not blow up. I think Dr. Drew and others have clarified that in past research.

Dead on right. How many times has this same matter come up ? Over and over and somebody must feel that their gun is so infirm that it will blow up if the slightest miscalculation is made . Enough, enough.

[Dean Romig]

Agreed Bruce and Bill - but we can choose to be responsible or we can choose to be irresponsible when it comes to what ammo we stuff into our various shotguns....

There are neophytes in the realm of old side-by-sides who join our ranks or come onto our various websites every day of the year and I think it borders on the irresponsible to indicate they can 'throw caution to the wind' and shoot anything they want in their recent acquisitions.

As for me, I will continue to advocate for caution.





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[Drew Hause]

I'm with Dean. Since none of us can know the abuse to which our maybe 120 year old guns have been inflicted, it would seem prudent to use reasonable due diligence to at least establish that the chambers/barrels have not been modified, and to use loads ballistically equivalent to those for which the gun was originally designed.
Parker Bros. probably knew what they were doing, documented the load with which the gun was patterned on the hang tag, proved every gun, and built in a significant margin of safety.
It HAS been proven that the pressures generated by turn-of-the-century smokeless loads were quite similar to today's if at the same payload and fps

Though opinions were offered, the cause of this blow up, to my knowledge, was never established by a metallurgical failure analysis
http://www.doublegunshop.com/forums/...=491058&page=1



A buddy was bidding against somebody's grandma at an auction in Liberty, Mo. on a Damascus barrel 16g Parker. Grandma won, and told him she wanted it for her grandson to use turkey hunting. She didn't believe him when he suggested that use with modern turkey loads would not be a good idea.

[Drew Hause]

Since this is a very frequent question, maybe in the "Help" section at the top of the Forum a "PLEASE READ THIS BEFORE SHOOTING YOUR PARKER" post could be generated? The FAQs seem to be overlooked.

I just added "Please review the General Information "Is my shotgun safe to shoot?" FAQ before using your L.C. Smith or Hunter Arms Co. Fulton shotgun." to the header of the LCSCA Forum.

[Ron Scott]

No wonder the neophyte is confused. In one place he finds Sherman Bell’s test results in the Winter 2001 DGJ article where he writes:

“With loads that are sensible in a light 2 1/2 inch gun, we see no dangerous pressure levels produced. I see no reason, related to safety, to modify an original 2 1/2 inch chambered gun to shoot 2 3/4 shells, if the 2 3/4 inch load you intend to use would develop pressure that is safe in that gun, when fired in a standard chamber.”


Then in another place he finds Larry Potterfield showing him how to lengthen the chamber of an antique Parker:

https://youtu.be/amBveFBnVgY