doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Baited Breath, Waiting for "Digs" Up-Date.

Rocketmon'(Iv'e been talking to a Scotsmon on the Island of Sky', Those Hairy Kilted Chaps really know their Gunmaking) The question that arose' was 'When did the Proof-Houses on the Merrie Island of St.George, start proofing each barrel submitted, with TWO PROOF LOADS...and my question still is"Why"? Maybe you have seen it published somewhere?? cc/dt

There are several reasons to proof a gun. In Mery ol', all new guns need be proofed. Europe requires that new guns also need be proofed, but since I once bought a rifle by a major Euro maker, and the damned thing would not chamber a round. I looked and the damned thing had never been CHAMBERED! It was, however, proofed! As it turns out, that particular nation only proofs a few out of a hundred guns. It would never happen in England as they never were much with bolt guns, so naturally, cannot be so trusted.

Of course, other reasons to proof a gun include when there has been a chamber lengthening, a honing beyond the proof limits, or when nitro proofing a Damascus gun. I don't know if the failed Purdeys may have been old Damascus guns with dangerously thinned and chamber lengthening barrels coming back for a nitro proof. That would make a lot more sense than brand new guns.

A bit on materials now. There are two different but very important steel strengths. One is Ultimate Strength. That is the pressure at which a piece of steel (barrel) will fail by blowing/cracking/splitting/etc. Another steel strength is Plastic Strength. This is the pressure where a piece of steel will expand to while under a load but return to the original shape. Over this amount, there is a plastic deformation, and the steel will be deformed. A barrel bulge is a form of this. The proof tests carefully measure the barrels at a number of critical areas before and after proof pills are fired. If there is any measureable deformation, the barrel has failed proof test. Of course, blowing a barrel is the worst form of failure. There is also the preliminary visual test by the proof house. The barrels fail if the barrels are loose to the frame, if they have bulges, or pits. They must visit the smithy and these things be fixed before the tests can continue.

Stuff happens (like the stainless Sako barrels in a certain serial number range of which at least 6 blew up). However, I would be very surprized if new Purdey barrels blew. It might make one send ones guns to Birmingham, instead.

Of course, this solves the question of which is better, LC's and Parkers or those Brit things. No LC or Parker has ever failed the London house. Proof positive, wouldn't you say, David?

Pete, I dont think you had an answer to my question.dt

Sorry, my sincere appologies. Jealousy got better part of me. Who knows I might loose an eye or injure my arm shooting my best clunker in NC this weekend. When one's number is up it's up.

David, I can only tell you that there is NO statistical reason to shoot TWO proof loads through a single barrel.

Pete the Mechanical Engineer

The rumours are of NEW guns blowing up and at least one old double rifle.

The Proof House sent us all a letter Feb 2007 (from memory)telling us that they were now firing double proof charges - they quote CIP regulations as a justification.

Lets remember many of them new London guns are leaving for points East of the Oder to places like Moscow, Ole' Leningrad,.... Our folks think "double proof" vodka is good and those weak puny English drinks ......

I was under the impression that for new guns the barrels were proofed in the white, to avoid the waste/destruction of costly work should something go "wrong"???
K.

Who said the barrels failed?

Suppose you need to design a pipe to withstand 12,000 psi. Because of life safety issues you multiply the 12,000 psi by a safety factor of 5 and get 60,000 psi. You then design the pipe to withstand up to 60,000 psi. Then you build the pipe and you subject it to a proof test of 24,000 psi.

I made up the safety factor of 5. I have seen them as high as 100 (cranes). I completely left fatigue stress considerations out etc...

Best,

Mike

Edit - Safety Factors are arbitrary to my mind. Based on experience and science and statistics I imagine.