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Ducks Rx, eeb, Glacierjohn, wannagohunting
Total Likes: 13
Original Post (Thread Starter)
#34328 04/05/2007 8:28 PM
by Steve Lawson
Steve Lawson
Is is safe and ok to use low pressure 2 3/4" 12 gauge shells in a nitro proofed gun with 2 1/2" Chambers? If so, what would be the recommended pressure to stay under? Thanks!
Liked Replies
by Jim Moore
Jim Moore

I will not tell anyone that it's safe to shoot longer 2 3/4" ammo in a 2 1/2" gun. I will however tell you that I reload to below 7000 psi in the longer hulls and shoot them in my 2 1/2" light game gun. I have been watching several boards for about 5 years and I have never heard of any problems with this practice. If you are concerned just buy the factory ammo for the peace of mind. That has to be worth something.

2 members like this
#608602 Dec 30th a 09:03 PM
by Drew Hause
Drew Hause
shrapnel: IMHO there are many on this Forum with the bona fides to provide accurate and reliable information
Actual strength testing of pattern welded barrels
and vintage steel barrels

John Brindle, author of Shotgun Shooting: Techniques & Technology published a review of Proof and Service pressures in Part 5 of his series in The Double Gun Journal, “Black Powder & Smokeless, Damascus & Steel”; Volume 5, Issue 3, 1994, “Some Modern Fallacies Part 5”, p. 11.
His estimated post-1954 but pre-CIP standard pressures by LUP converted to piezo transducer PSI

..............Standard Service.....Max. Service.....Proof
12g 2 1/2”.....6,800 psi..........8,800 psi..........12,250 psi
12g 2 3/4”.....7,800 psi..........9,800 psi..........14,050 psi

Great Britain adopted the 1969 Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives standards March 1, 1980 but continued using Lead Crushers to measure pressure until 1989.
The CIP transducer “Maximal Statistical Individual Pressure” is 850 BAR = 12,328 PSI for a “Maximal Average (Service) Pressure” of 740 BAR = 10,733 PSI, and “Mean Proof Pressure” of 930 BAR = 13,924 PSI.
900 BAR is for a “Maximal Average (Service) Pressure” of 780 BAR = 11,313 PSI and Proof pressure of 1020 BAR = 14,794 PSI.
2 members like this
by Little Creek
Little Creek
I have two 65mm chambered 16s. One of them weighs 5# 11 and I shoot reloaded light 2-5/8" 7/8 ounce and light 1 ounce factory loads in the gun. I don't see any difference in the fired shell relative to another gun with factory 2-3/4" chambers. I am considering lengthening the chambers in at least one of these so that I can feel better about using 1-1/8 ounce loads for pheasant.

These guns were purchased used and I'll bet they have been used a fair amount with 2-3/4" loads. Not everyone reloads or buys RSTs.
1 member likes this
by David
Recently there was a lengthy discussion of forcing cones and lengthening them. I believe that reaming a chamber has the potential to thin the barrels in the most dangerous place while lengthening forcing cones does not. That is not intended to imply that lengthened forcing cones have any real value. Are these guns from England? If so reaming the chambers invalidates the proof while forcing cones is a grey area. If they were my guns, I would not ream the chambers, but find suitable low pressure loads commercially even if they're 2 3/4.
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by Stallones
I think any of us that have read Sherman Bells articles in DGJ
as well as some of the English articles feel very comfortable with "2 3/4" ammo in 2 1/2 chambers. I use STS cases and 22.5
gr. 7625 with 1 oz of shot and they are low pressure and fine. As stated many times there is only about 100 psi increase and of course the STS and WW are about 2 5/8 in length.
1 member likes this
by Drew Hause
Drew Hause
The Winter 2001 Double Gun Journal has the article by Sherman Bell called "Finding Out for Myself" Part V "Long Shells in Short Chambers".

After extensive testing carried out in a very professional manner he concludes:

"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!

I personally perceive slightly greater recoil with my 2 9/16" chambered 16g LC than with my 2 3/4" chambered 16g LC using the same 2 1/2" shells, and for that reason the brls are with Dan Lammers getting the chambers lengthened right now.
1 member likes this
by Geno
Anybody putting 70mm ammunition in a 2 1/2" proof stamped shotgun is a fool in my opinion.

Then I'm a fool. Sometimes I use light 2 3/4 case loads in 2 1/2 chamber English guns, because UK chamber dimentions standarts are not so tight as German ones for example. Also it depends on forcing cone length and bore gauge. 12G, 13/1 and 13G are o'key in this case.
I feel I'm pretty much educated to check guns and to choose right ammo for these guns. Sometimes 2 1/2" case doesn't mean at all it could be used in 2 1/2" chambers.
Who says use ONLY 2 1/2 ammo in 2 1/2 chambers probably a fool, because ammo has to be proper to particular gun in many aspects and not only in case legnth.
1 member likes this
by Alder adder
Alder adder
Since I am a fool, I wouldn't hesitate.
I see this load as a very sensible choice.
My personal 12 gauge load for 2 1/2" brit doubles
consists of 24 grains of SR 7625 in a Win AA or Rem STS case, win 209 primer and Win AA or Claybuster wad.
I don't recall the exact ballistics as I have been using this load successfully for ten years. It ias right out of the old IMR booklet. It is a bit dirty as most slow burning powders are. Using less than one ounce of shot with this powder produced duds for me.
1 member likes this
by Chuck H
Chuck H
I've heard a lot of opinions in this thread. Some opinions, by proponents of 2 3/4" shells in shorter chambers, are based on Bell's work and extrapolated to their reloads. While Bell provided some informative data, unless I were using the exact loads he tested, I'd be uncomfortable.

I think Bell simply cracked the door open for a promising outcome of those wishing to further pursue testing of their selected long shell/short chamber load.

I realize that there is a vast diversity of knowledge/education/experience here on this bbs, but have yet to hear that anyone has pressure data that indicates the subject practice is unsafe. I work with hundreds of engineers and often represent many of them in front of our regulatory agencies. They are all educated and knowledgeable people...in their respective fields and within their education and experience. I challenge them all the time, because they can't know everything, they are people and put on their trouser's one leg at a time like everyone else...they can err.

Sure, cramming a WallyWorld modern 2 3/4 load into a shortchambered 100 yr old gun is potentially unsafe and without a doubt foolish.

I have explained my approach to obtain direct data on this in my first post on page 1 of this thread. I think those that are pursueing the loading of long shells for short chambers should obtain pressure data of their particular load in the chamber dimensions they will be using. It's not a huge investment.

So, I'll say it another way; If someone has direct knowledge that this is an unsafe practice to shoot 2 3/4" shells in a 2 1/2 -2 9/16" chamber, please share. To me, this means actual pressure data. If any of our membership out there has real pressure data to share, I think it would truly be a service to our community.
1 member likes this
by Joe Wood
Joe Wood
It has been noted in this discussion that American manufacturers often chambered short even though longer hulls were in use. I find this typical hang tag from Parker to be quite informative. Look at the chamber length and then the recommended shell. And these were from the days of thicker paper hulls. Today's plastic hulls are much thinner, offering even less constriction in the forcing cone. For me, I'll go with what the old men suggested. They wanted the hull to open up well inside the forcing cone to provide a better gas seal. Even though today the plastic wad is universal I think the same principle applies.

1 member likes this
#608599 Dec 30th a 07:46 PM
by shrapnel
The Internet and forums on the Internet are not reliable sources for much valuable information. So I will add to that with my own experiences.

I used to visit with Bill Heckman when he had his shop in Livingston, Montana, about Damascus guns and how strong they were. He told me how they proofed guns and and I was amazed at how simple that process was. They put the gun in a brace and test it with their proof loads that are developed for proofing guns at a pressure above what the gun is actually designed for. II the gun didn't blow up, it was in proof.

I took several Damascus guns to him to get his opinion on shooting them with smokeless ammunition and what to expect. He told me that the good Damascus guns were as strong and even in some cases, stronger than the fluid steel barrels of the same era.

Since then, I have shot lots of older shotguns with Damascus barrels and had no issues at all. Before doing so, I did check to see they were in good working order with good wall thickness in the barrels and no rust or pitting.

I have shot plenty of 2 3/4 inch shells in my Webley SXS that has 2 1/2 inch chambers and had no ill effects at all. I do keep plenty of 2 1/2 and 2 inch shells around and shoot them exclusively in those shorter chambers as that is the best way to shoot them.

I have seen blown up shotguns that were from other reasons than 1/4 inch difference in shell length. The best rule of thumb is to shoot what you are comfortable with and if you are afraid of blowing your gun up, by all means use shorter shells.

I would also bet that the pressure is less likely to damage the gun as much as recoil would shake it loose.

[Linked Image from i.imgur.com]
1 member likes this

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