doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Proof failures

Dig,
What you describe actually did used to happen in Motor racing, especially when a driver was having an identity crisis he would disappear around the back of the circuit and deliberately detonate a perfectly good engine. That was until engine management and telemetry became common.
Perhaps the Proof houses need to check pressures nearer the muzzle in light of these current problems.
One thing is for sure these guns that are failing are not the weakest barrels available and have not suddenly all become necessary to be proofed at the same timescale. So we have to question, The test procedure, the test components, the test operatives. Something is definately wrong and IF these valuable artifacts are being ruined by incompetence then recompense should be sought. We both know that will never happen but I am sure the Guardians should be made aware of our concerns.

We are short on facts here, but my money is on shot balling or bridging. I can't imagine a powder able to develop barrel bulging pressure at the chokes without chamber damage. Bulging right in front of the chokes sounds like a gas hammer caused by some event, like balling of bridging, that occurs as the shot encounters the choke constriction and is somehow limited in its ability to flow like a fluid.

Dig, I am really sorry to hear of the proof failure. Any chance this is just coincidence or was it a sound barrel?

I have spoken to others about this matter in the last day or two and it would appear that Birmingham have not been suffering the same rash of failures as London and neither were they aware of London's problems.

Another significant member of the gunmaking community smiled ruefully and commented that nothing much has changed. What he was apparently referring to was the history of a lack of communication and some fairly childish one-upmanship over the centuries between our two august institutions.

I agree with Don.

Barrels that are simply back for a reproof should not exhibit this.

I can not imagine a powder or charge common to small arms that would still be building pressure 26+ inches from the chamber. The only thing that comes to mind would be a howitzer.

We have been instrumenting barrels for nearly 120 years. We know full well how things behave. Too much black powder and it gets blown out unburned. Too much smokeless or too fast a burn rate and you rupture the chamber.

Are they testing with some alternative (none lead) shot in an attempt to lower the over airborne lead at the proof house?

Pete

Reading the rules of proof introduction leaves us in no doubt that oneupmanship has existed for centuries. But this childish behaviour does not help Diggory and others who suffer a loss whilst entrusting valuables to 'experts'.
Don & PeteM thank you for your input and observations, as I have said, there will be a logical explanation and then someone will say "Who'd have thought that". The sooner they find out the better for everyone.

I can't of course speak for every gun ever built, but all that I have ever checked have had a slight increase in wall thickness as the choke was approached. Thus I have never found the thinnest point of the bbl wall to be at the juncture of the bore to the choke cone, but a few inches back. This would definitely seem to negate it being a simple change of powder.
Whatever the ultimate cause it surely seems the shot charge is being "Checked" by the choke & thus having the effect of an obstruction. This would account for the "Bulge" behind the chokes as the check would occur on the front of the shot column hitting the choke.
They haven't started proofing with a bore size ball have they??

Do they use shot when they proof a gun?


Thanks

OWD

Did some probing today. I'll let you know what kind of responses come back on this. This latest glitch cost me �3000 this week!

I am sorry for your loss. Has all the rash of failures been in the London proof house or at both? Those in the trades must be dreading proofing like a bomb disposal expert with two sprained thumbs. Hope the problem is figured out soon or the proof house in question should be avoided like the plague.

I'd suggest making sure nothing stupid is happening like something being stuck down the muzzle/run through the bore such that occasionally a bit is left to act as an obstruction.

Second,I'd make sure thate is no wad issue that could contribute to shot balling.

Third, I'd look for any coating on the shot that could contribute to said shot not flowing and/or having an unusually high friction coefficient for surface to surface contact.

Forth, I'd check shot size inuse and make sure it is #6 or smaller as larger shot is more prone to bridging.

Last, if two, or more, proof loads are being fired, I'd check for shell bases coming loose and lodging in the choke section.

If one of those doesn't get it, I'll have to think some more.