doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel Burst

The conspicuous bulge near the breech-most end of the split sure looks like an obstruction to me. For sure, significant yielding took place before ultimate rupture.

The highest pressure at 16" from breech (eyeball estimate assuming 30" bbls), in my modest collection of pressure curves, is just over 1500 psi. Even if the walls are down to 0.020" (and they look thicker) we're talking ~ 28,000 psi hoop stress there. That's more than I'd want in old bbl steel but not likely to cause yielding, IMHO. Cyclic fatigue, possibly, but the big bulge indicates to me it happened in very few cycles (unlikely) or just one, probably.

Gentlemen! Thanks again for your valuable advice.

Here is an image with best possible measurments, that could be made with vernier calipers. I tried to measure at very edges, so that the curve of wall should not effect the readings.


@Greg
Yes I am in Pakistan. I am not sure of Shaheen standards, there is no mention of it on the boxes. 31 gms load is mentioned. Will soon post loads of all other shells used.

@Roy
What was the difference between 3 grades?
A friend has Burrard's book and I will get it for diagnosing method.

Any comments on barrel thickness?

0,6 and 0,5 mm - it's big differences and might be seen as uneven surface and spots inside bores using light-and-shadow method, but in barrel before burst. Now it's very hard to say what was the reason of such irregular mesurements, but I vote for burst and steel tension as result of the burst.
Any way I have to say, that 0.020" - it's d*mn not enough for the shhoting with modern ammo such as S&B for example, I know this ammo very well and this ammo is pretty hot and very often the pressure is higher, than CIP standart recomends.

Certainly there was a great deal of metal stretching before the burst, so I doubt that there is any real evidence in your measurments of thickness at the failure. I would check the thickness at points 1 inch before and 1 inch after the burst where the metal has not been stretched.

Saad,

You posed this question a few pages back:

"Almost all replies indicate that there was an obstruction. Now my questions is that what chances a modern, in-proof, un-honed, un-repaired and well kept gun has against a blow like that, in comparison to a near junker."

Locally, a couple of years ago two almost new 600 series Berettas had barrel bursts. One of the hunters was a surgeon that sustained a serious hand injury. Engineers from the factory flew down, there were lawyers involved (teeth barred and as can be expected Beretta was really concerned. Extensive tests were made. In the end it was determined both blow ups were due to obstructions. One was caused by a failed shell that came apart. The other, I believe, by mud.

I hope this answers your question. Someone adviced about checking the bores after each shot before reloading (surely not an extended practice among shooters in general). We should take heed.

JC(AL)

Greg: you ought to take this show on the road. I'm still chuckling.

I have to warn everyone about dangerous common mistake every burst in the middle of the barrels is definetly result of obstruction.
The min wall thickness of this particular gun was DANGEROUS!
I know at least one English gun, that blew up the same way without any visible reasons. All empty shells been inspected then. The gun was hardly used and bores well honed.

Gennady,

If "hardly used" why were the barrels "well honed"?

I'm thinking Geno means "hardly used" as per the Yank vernacular "used hard and put away wet" rather than the sense of very little use. Looks like the usual 50/50 non-consensus on causation. Tossup between proximate and final cause.

jack