doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Would You Buy an Out of Proof British Shotgun?

The problem, eightbore, is that your typical US factory 2 3/4" load may very well generate a higher pressure to start with than the loads for which an American short-chambered gun was designed. (It's not the length of the hull as much as it is what's in it.) By the time you add in the extra pressure that comes as a result of a slightly longer hull in a slightly shorter chamber--and in at least one or two of Bell's tests, the increase was around or over 1,000 psi--then you may be putting your foot into dangerous water. I don't worry about low pressure reloads in 2 3/4" hulls being fired in short chambers. But with reloads, especially in 12ga, we can work for pressures that are well below the service pressure for which the gun was designed--thus leaving enough safety margin to cover any increase in pressure resulting from the longer hull. Both Greener and Thomas stress, however, that firing the higher pressure 2 3/4" factory loads in short chambers is a bad idea.

You could ship it to Briley and have it rechambered to 2 1/2.
danc

If you re-chamber it to 2 1/2" it would still be out of proof as the proof becomes invalid when the barrels are materially altered - this includes chamber liners. I re-proof guns routinely - we generally re-proof all guns for 70mm now, the proof pressure are the same for 65mm and 70mm and lengthening the chambers makes the options a bit easier, especially for those travelling.

Dig, somewhat confused by the above. As I understand it, 65mm guns can only be standard proof (the old 850 bars). 70mm guns can be standard proof, but you can also request magnum (now Superior) proof, can you not? And if the gun is standard proof, even if 70mm, the service pressure is lower (10,730 psi) than SAAMI standard service pressure (11,500 psi) here in the States. Thus, would not a 70mm standard proof gun still have issues with American factory 2 3/4" shells?

Diggory, can a 2 1/2" chambered gun be submitted for 70MM proof? Regardless of what Larry is trying to say, drilling a perfectly safe 2 1/2" gun out to 2 3/4" is just money out the window.

At re-proof, the chambers are measured. If they are 2 1/2", they will be proofed and stamped 65mm STD. If you lengthen the chambers to 2 3/4", they will be re-proofed and stamped 70mm STD.

65mm standard proof and 70mm standard proof are the same pressure. 70mm Superior proof is generally only used in very heavy 'magnum' wild-fowling guns.

I am not familiar enough with American ammunition to be clear on what you can buy which is suitable.

All 70mm ammo here is OK for use in standard proof guns with 70mm chambers unless marked 'magnum;.

That does not mean that you won't wear out a gun and or yourself if you choose to shot punchy, heavy loads through a light gun. Just because the chamber has been tested to withstand a certain load does not mean it will be a good choice for regular use in your gun. You still need to exercise common sense when choosing a load.

Small bore,
Can you solve this conundrum?
I have always had a special interest in early British hammer guns. Guns made pre 1868 were proof tested and proof marked to different standards to post 1868 guns.
For example a pre 1868 gun 12 bore stamped 13 G at proof could have a legal bore size in the range .700-.728 diameter.
Post 1868 the bore size were identified by diameter and stamped on the barrel as follows:
13 .710-.719
13/1 .719-.728
12 .729-.740
My 12G Daw of circa 1861,proof stamped 13 G has bore size of .725
Is this gun still in B.P. proof Bearing in mind that it was proof tested under the rules applicable prior to 1868?

Small bore, it would be a great help for some of us if you could provide us with the complete London rules of proof 1855-1868, along with bore diameters for each gauge marking. Please.

Dig's book
http://books.google.com/books?id=lvBk8df8PjUC&pg=PA139&lpg

Possibly he would be kind enough to reproduce the chart here.

Maybe Dave would make this wise advise a permanent sticky

"You still need to exercise common sense when choosing a load."

European cartridges have to be proof tested also (random samples from a batch) to see that they fall within safe limits compatable with the pressures for which the gun was proofed. Such ammo boxes will be marked with the CIP logo. Certainly the older American made Winchester AA cartridges imported to Britain and the Remington RXP's in the 1970's were found to be well over the safe limits for 2 3/4" chambered English guns. American ammo is quite punchy; or at least was then. Even if you have an English 2 3/4" chambered gun I would be cautious about using non-CIP ammunition. Lagopus.....