doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com The Value of Proof

Looks like 70 mm chamber by the proof house note.....that was probably the 1st mistake, reaming/lengthening the chambers on a gun that old. Then, 2 3/4" proof loads.....Yikes! No wonder the old girl failed.

I think the new proof procedures are ruining too many guns which should have passed proof. I understand it's the way it is and the law is the law but to change the rules this much just puts a lot of guns at unnecessary risk. I guess I'm like a lot of people and wish they had two standards so period hubs could be proofed today like they were designed to be proofed at when made. But they don't so it's roll the dice and see what happens. Kind of makes you sick when a gun fails that you'd expect to pass but I'm sure it's always been like that.

Don't forget, we are interested in saving/using the fine old guns; but there, the ones that make the rules have been doing everything they can to do away with guns, for years.
Mike

It seems to me that the whole purpose of government sponsored proof is to insure that the gun will be safe for the least informed shooter who may use it. If layered proof standards were adopted to prevent the destruction of older less strongly built guns all the public would know was that it passed proof. They would shoot whatever shells they had available, when what they should be shooting was low pressure...Geo

The choice, then, would seem to be between having fewer dumb shooters or fewer fine guns? I know which one I am going to pick...

What is the source that indicates more older guns are failing proof. I'm interested in learning what the Birmingham Proof House has to say about revised procedures and failure rates.

If? I thought the proof markings were 'layered' now. There are so many questions here about folks asking what proof marks mean. Are the marks really so clear. If a gun is marked 12 ga., now the general public is protected from harm by using anything that comes out of a box marked 12 ga.?

I think the topic started off by the original fellow noticing that some procedure at the Birmingham proof house has changed recently which translates to more proof failures. Was the change arbitrary for a preferential purpose, or was there evidence of public harm from inadequate proof testing?

The only layers of proof I'm aware of are black powder and smokeless. Well, I guess there is a 'new' steel shot proof. The chamber length is on the gun or is readily measured...Geo

There are a few misconceptions here concerning proof/reproof. Mr. Barclay didn't mention whether the gun had been reproofed previously at some time. However, although it's much more likely the gun started life as a 2 1/2" gun, we don't know that for sure. But since the proofhouse tag says 12/70, then that's either what it was to start with, or else--somewhere along the line--it had already passed one reproof with the lengthened chambers. Otherwise, it would not have been a case of whether Toby WANTED to have it reproofed just to be on the safe side. If the chambers were lengthened from 2 1/2" to 2 3/4" and the gun had not been reproofed, then it would be illegal for him to sell it without submitting it for reproof.

You won't find chamber length marked on 1880's guns unless the gun has been reproofed. Chamber length wasn't a required proofmark until 1925.

As for the pressure of a current reproof, it is my understanding that even a 2 3/4" gun, if the owner so requests, can be proofed at the "standard" level (rather than the much higher superior proof level). Per the Birmingham Proofhouse, that is something a bit less than 14,000 psi as we'd measure it in this country. British/CIP standard proof guns use shotshells that generate pressures of slightly less than 11,000 psi. So while a standard proof load is indeed an overload, there isn't nearly as much of an overload as there is between the standard service pressures of American shotshells and the pressures of American proof loads. 12ga SAAMI service pressure is 11,500 psi, against a proof pressure of something in the 18-19,000 range.

Current British proofmarks are pretty clear. If the gun is standard proof, it's marked STD--and you use the shells suitable for a standard proof gun. If it's superior, the marking is SUP--and hotter American shotshells will work just fine. Older British proofmarks can be somewhat confusing unless you know how to decipher them.

Buzz, the pressures for 2 1/2" proof are exactly the same as for 2 3/4" proof. The only difference between the two proofs is the length of the chamber. If I had a barrel failure in the critical area where the chamber has been lengthened, I would of course blame the lengthened chambers but that has never happened to me. Failures have to date all been rivelling of the central part of the tube (often in areas of less than ideal MWT) or bulges at the choke forcing cones (usually with choke constriction of over 0.020"). Once or twice a weak action has come off face but this has usually been a thin, early breech loader such as a converted pinfire. A couple of times the lumps have come loose and had had to be re-brazed.
L.Brown, This gun was heavily pitted but with very good MWT's and substantial metal in the chamber area. To remove the pitting, the barrels had to be lapped to beyond their proof size so it HAD to be re-proofed. Given the nature of the 2 1/2" and 2 3/4" proof tests (see above), it was a no-brainer to lengthen the chambers. So when the gun was submitted for proof, it had 70mm chambers, the gun would have been measured at 'view' and when the gun failed (or passed) the paperwork would record it as a 12/70. It would not have to have ever passed 70mm proof to be ticketed as such.
Actually, all proof is done at the 'Standard' level for the chamber length UNLESS you request 'Superior'.
Craigd, The reason why proof is valued by most shooters in the CIP area is that we CAN go into a gun shop and if the box of cartridges says it is suitable for the chamber length of our gun, we can use it with impunity. Obviously, once the gun leaves the CIP area, eg goes to the USA, there is no such standard and ignorance of what a suitable load might be could get someone into trouble. I make no criticism of the situation in the USA, I just try to manage the risk as best I can.