October
S M T W T F S
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
Who's Online Now
3 members (SKB, 2 invisible), 89 guests, and 14 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums10
Topics36,801
Posts520,779
Members14,212
Most Online462
Aug 5th, 2016
Previous Thread
Next Thread
Print Thread
Page 2 of 3 1 2 3
Joined: Jan 2006
Posts: 8,813
Likes: 113
Sidelock
***
Offline
Sidelock
***

Joined: Jan 2006
Posts: 8,813
Likes: 113
We now have excellent data regarding turn-of-the-century shell pressures, which, with Dense Smokeless, were very similar to today's
https://docs.google.com/document/d/1F2sQuPm05IE4VWYYnCkvuXmYEzQoWd_SQgaAfUOZEFU/edit

Jon: are you aware of any modern pressure data regarding the pressure increase in using long shells in short 20g or 16g chambers?

This is all that I have found, and it's 110 y/o
“The Long 20 Bore Cartridge”, The Field in Forest & Stream, October 17, 1908
https://books.google.com/books?id=ejQevDPMUIYC&pg=PA630
2 3/4” case with “Schultze” Bulk Smokeless (42 gr = 3 Dr. Eq.)
The standard 2 1/2” case was loaded with 33 gr. “Schultze” = 2.36 Dr. Eq. (about 2 3/8) with 13/16 oz. shot.
36 gr. = 2.57 Dr. Eq. with 15/16 oz. = 4.65 tons = 14,504 psi (using Burrard’s formula) / 20 yd. velocity 1000 fps. That is the post-1924 Belgian 20g proof pressure.
37 gr. = 2.64 Dr. Eq. with 7/8 oz. = 4.54 tons = 14,134 psi / 1040 fps
35 gr. = 2.5 Dr. Eq. with 13/16 oz. = 3.45 tons = 10,472 psi / 1068 fps

It was Progressive Burning DuPont Oval, developed for the 1922 introduction of Western Cartridge Company’s 12g ‘Super-X Field’ 2 3/4” 1 1/4 oz. 3 3/4 Dram Equiv. shell, that enabled the use of large payloads at lower pressures.

1 member likes this: Glacierjohn
Joined: Mar 2002
Posts: 7,199
Likes: 144
Sidelock
**
Offline
Sidelock
**

Joined: Mar 2002
Posts: 7,199
Likes: 144
Sorry Drew I am not aware of any real numbers. I have seen speculation about this but no real solid numbers. For that reason I have arbitrarily set my maximum 20 gauge classic double pressure level for 20, both short and 2 3/4” at 8,000 psi. From everything I’ve gathered about British proof levels I should be very safe. It is interesting that my Remington 20 empties all measure 2 9/16”. So for compression formed hulls I do use them in my 2 1/2” chambered guns. If loading AA or Federal type hulls I trim them to 2 1/2”. Much easier to find lower pressure loads in Federal or Cheddite type hulls.

2 members like this: Glacierjohn, Drew Hause
Joined: Nov 2021
Posts: 114
Likes: 17
AGS Offline
Sidelock
*
Offline
Sidelock
*

Joined: Nov 2021
Posts: 114
Likes: 17
One thing I haven't seen mentioned is how this affects some of the older Parker's. In the hammer gun era, a lot of the 10's and 12's were chambered for brass shells. They came in two sizes, one smaller than normal and one regular chamber diameter. I just bought an 1880 10 ga set up this way for the "A" size shell with normal dimensions.These guns were ch.ambered to exactly the open shell dimension with a step down to the barrel diameter and no forcing cone at all. I did a lot of careful measuring and confirmed this. Parker was apparently rather proud of this system and stated it gave the best performance. I suspect a shell even slightly shorter than the chamber would give a significant pressure spike.

Joined: Feb 2008
Posts: 511
Likes: 1
Sidelock
**
Offline
Sidelock
**

Joined: Feb 2008
Posts: 511
Likes: 1
Those old guns were chambered to work with thick-mouthed paper shells. Mike a once-fired paper shell and then mike an AA or STS and you will see that the case mouth on the newer shell will not run interference with a 2.5" chamber.

Joined: Nov 2019
Posts: 101
Likes: 5
Sidelock
OP Offline
Sidelock

Joined: Nov 2019
Posts: 101
Likes: 5
Originally Posted by Ithaca5E
Those old guns were chambered to work with thick-mouthed paper shells. Mike a once-fired paper shell and then mike an AA or STS and you will see that the case mouth on the newer shell will not run interference with a 2.5" chamber.

I’m not sure I’m getting you. Are you talking about the thickness of the paper unfolded, being thinner now, so even a little overlap extension past the chamber doesn’t create too much pressure?

Joined: Jan 2002
Posts: 11,131
Likes: 26
Sidelock
**
Offline
Sidelock
**

Joined: Jan 2002
Posts: 11,131
Likes: 26
Originally Posted by limapapa
The consensus on the PGCA website seems to be that Parker cut its chambers 1/8 in shorter than the expected shell length, feeling that the overlap into the cone sealed the shot charge better. Thus, 2 5/8 in chambers were for 2 3/4 in shells. That said, I shoot 2 3/4 shells at 1165 in my 2 9/16 inch 16 gauges without incident. If the barrels are sound, and the chambers original, you should be OK.

Intentionally short-chambering guns in order to improve patterns was a fairly common practice back when everyone was shooting paper hulls and fiber wads. I have a couple American Rifleman articles from the 30's that discuss it. The author had worked in the firearms industry since the 1890's. He had a 12ga Marlin 90 made with 2 1/2" chambers. Shot patterns using standard 2 3/4" shells. Then had the chambers lengthened and repeated the pattern testing. His patterns ran something like 8% better when using shells that were slightly longer than the chambers. Apparently trap shooters of that era were well aware of that and took advantage of it by making sure chambers were slightly shorter than the length of fired hulls.

Of course today, with plastic hulls and wads that do a better job of protecting the shot charge, there's no advantage to shooting longer hulls in shorter chambers. Nor, however, is there any particular disadvantage . . . AS LONG AS THE PRESSURE GENERATED BY THE LOAD IN QUESTION IS NOT SIGNIFICANTLY HIGHER TO START WITH THAN THE PRESSURE FOR WHICH THE GUN IN QUESTION WAS DESIGNED. The British regularly shoot 67/67.5MM shells in guns with 2 1/2" chambers. It works fine because those shells are loaded to appropriate pressure standards. In contrast, using off the shelf US ammo can be risky because our standard 12ga service pressure is already somewhat higher than the CIP (British/European standard)--by about 800 psi. Add to that the fact that Bell recorded increases in pressure that were mostly only a few hundred psi, although in one case the pressure increased by more than 1,000 psi.

Result: If you're shooting a 12ga and reloading standard American 2 3/4" hulls through a gun in good condition, you shouldn't have a problem as long as you build in a safety margin. It's very easy to come up with reloads, for shot charges up to 1 1/8 oz, at pressures under 8,000 psi.

1 member likes this: Glacierjohn
Joined: Jan 2002
Posts: 12,117
Likes: 306
Sidelock
**
Offline
Sidelock
**

Joined: Jan 2002
Posts: 12,117
Likes: 306
You can even find 2 3/4" factory loaded shells that are in the 6000 psi range .................. B & P Comp Ones.


May God bless America and those who defend her.
Joined: Jul 2006
Posts: 1,159
Likes: 3
Sidelock
****
Offline
Sidelock
****

Joined: Jul 2006
Posts: 1,159
Likes: 3
The practice of lengthening the chambers of English guns from 2 1/2 to 2 3/4 accompishes only one thing,It rendered the gun out of proof!
The practice of lengthen chambers dates back to the time when a 2 3/4 shell actually measured 2 3/4, These old shells had card tubes and a rolled turnover.The card tube had a wall thickness greater than todays plastic shells which also possed an increased safety risk if an atempt was made to load them and shoot them in in a 2 1/2 chambered gun!
In reality it was all but impossible to close the action of a 2 1/2 chambered gun with a shell that actually measured 2 3/4 !
It was this issue that prompted ill informed owners to demand that their gunsmiths extend the chamber length of their guns to make them useable!!
The closed length of todays 2 3/4 plastic shells is approximately 2 1/4 inches,after firing it measures approximately 2 5/8 inches.bearing in mind the thin wall of plastic shells and the pressence of a forcing cone from chamber to barrel bore there is virtually no constriction on discharge. I believe it was Burrard that said , "No cartrige case ever caused a barrel failure."
It is the pressure ceated by the weight of the charge &wads in combination with the explosive force of the charge including the the cap, that creates the pressure in the gun barrel
English guns with 2 1/2 inchambers are proof tested at a lower presuure than guns with a 2 3/4 chambers
Those considering extending the length of 2 1/2 chambered gun to 2 3/4 inches ,should ask themseves, Dose removing metal from the barrels of my gun increase their strength or dose reduce the factor of safety?
In 60 years of gun collecting i have seen 100;s of Fine guns put out of proof and in some instances ruined by chamber butchery.

Last edited by Roy Hebbes; 12/14/21 10:28 PM.

Roy Hebbes
1 member likes this: eeb
Joined: Jan 2002
Posts: 8,867
Likes: 56
Sidelock
*
Offline
Sidelock
*

Joined: Jan 2002
Posts: 8,867
Likes: 56
roy, give us some numbers...

what is barrel wall thickness in front of chambers that you consider minimum for safe shooting in a fluid steel barrelled gun...

old ed always liked .090...which is the standard i use...


advocating doublegon happiness...via 90/30 guidelines...
Joined: Jan 2002
Posts: 11,131
Likes: 26
Sidelock
**
Offline
Sidelock
**

Joined: Jan 2002
Posts: 11,131
Likes: 26
It's worth noting that a 2 3/4" shell only measures 2 3/4" AFTER IT HAS BEEN FIRED. Back when I first looked into the long shell/short chamber question, I compiled a pretty impressive collection of once fired nominal 2 3/4" hulls. While some of them came pretty close, all measured somewhat shorter than 2 3/4".

It's difficult to find very many vintage American 12's that are as light as many British 2 1/2" 12's. I have a William Evans 2 1/2" 12 made in 1901, with 30" barrels. Weighs 6/5 on my postal scale. One likely reason very few American 12's self-destructed after having chambers lengthened to 2 3/4" is that they were made heavier to start with than British 12's. While I have no interest in rechambering my Evans and submitting it for reproof, there are plenty of British guns that have had their chambers lengthened and have passed reproof.
My Evans, with its unaltered 2 1/2" chambers, closes with ease on once fired Remington Gun Club hulls.

Page 2 of 3 1 2 3

Link Copied to Clipboard

doublegunshop.com home | Welcome | Sponsors & Advertisers | DoubleGun Rack | Doublegun Book Rack

Order or request info | Other Useful Information

Updated every minute of everyday!


Copyright (c) 1993 - 2022 doublegunshop.com. All rights reserved. doublegunshop.com - Bloomfield, NY 14469. USA These materials are provided by doublegunshop.com as a service to its customers and may be used for informational purposes only. doublegunshop.com assumes no responsibility for errors or omissions in these materials. THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANT-ABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. doublegunshop.com further does not warrant the accuracy or completeness of the information, text, graphics, links or other items contained within these materials. doublegunshop.com shall not be liable for any special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of these materials. doublegunshop.com may make changes to these materials, or to the products described therein, at any time without notice. doublegunshop.com makes no commitment to update the information contained herein. This is a public un-moderated forum participate at your own risk.

Note: The posting of Copyrighted material on this forum is prohibited without prior written consent of the Copyright holder. For specifics on Copyright Law and restrictions refer to: http://www.copyright.gov/laws/ - doublegunshop.com will not monitor nor will they be held liable for copyright violations presented on the BBS which is an open and un-moderated public forum.

Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.0.33-0+deb9u11+hw1 Page Time: 0.099s Queries: 39 (0.075s) Memory: 0.8570 MB (Peak: 1.8991 MB) Data Comp: Off Server Time: 2022-10-02 12:47:56 UTC
Valid HTML 5 and Valid CSS