doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Lucky....

Here's a question...

Is a there a way to calculate how much energy it might take to produce the observed results here?

Assume a volume the size of a 12ga shell, sealed all around except for a .729" vent.

How much and of what would be needed to raise the pressure to the point that this sort of failure would happen?

What are we guessing? 50,000 psi?

Is it even possible?

If the owner of the destroyed shotgun ever shows up, I would bet good money he used the wrong powder.
Newish gun
No mods
Well known quality brand
Handload
Hmmm...


People make mistakes. I have seen a number of blown chambers, and everyone was either excess machining forward of the chambers, or inadvertant use of the wrong powder.

If you profile the people that have these malfunctions, it is seldom the new, paranoid, beginner at reloading, that only uses published data.

Just my view of course.

There is a local skeet place near here. There a approximately 2 million rounds shot a year there if I remember correctly. They have had two guns blow a barrel over the last 20 years. Both were hand loads.

In a common overpressure of a cylinder, you'd expect to see one area fail and open, releasing the pressure. This would almost without a doubt be the area that is the weakest area, i.e. an area compromised by a flaw or design feature. If you look at this failure, it failed on both sides simultaneously. It's unlikely that both sides are perfectly equal in strength and, to me, this suggests that the pressure was so high, so quickly, that both sides failed together before the weaker side could fail and vent the pressure. This is the only overpressure failure posted here that I can recall in my short memory where there was a symetrical failure like this. But I could be wrong.

If it was the wrong powder, it would have shown up earlier, assuming this wasn't the first shot. And assuming he didn't load the shells with a dipper.

It's pretty impossible to use the wrong powder just once, at least the way my MEC works. You can't double charge a round unless something really weird happens to the charge bar, which is possible, but the loader would notice it's harder to crimp.

I think it's a mystery with a solution that's going to be impossible to solve. Just one of those things that science, not gun guys MIGHT solve, if any were interested in studying it.

The wrong powder CAN do it.

An old pal of mine, who has been reloading since he was a kid, once made up a box of turkey loads with 1.5 oz. of shot.

Get this... his inattention was so complete, he used Green Dot instead of the IMR stick powder he intended.

The end result was a demolished 11-87, which amazingly failed on the second shot. He did have to hand cycle the action, since it was a bit 'sticky'.

The only surviving part was the buttstock. The bolt handle was found out by the turkey.

The problem could be from a reversed charge bar, where you're loading 1 oz of powder and 15 gr. of shot instead of 15 gr. powder and 1 oz of shot.

I think it would bear looking into.

2-Piper,I would agree that the accidental insertion of a 28 G shell in a 20G gun could result in the obstructional burst pictured.Burrard in Volume 3 of his book,The Modern Shotgun",pages 380-381 describes this possibility and states;"From the very nature of the obstruction the burst must always occur a little distance in front of the chamber cone."
Exactly the failure seen in the gun pictured.Obstructional bursts create a wave pressure that is much higher than that developed in the normal discharge of a shell in a barrel free from obstructions.We can see the resultant pressure increase totally destroyed the gun.What a lucky escape!

I recall a couple of reloading related stories regarding perported blow-ups; one of a guy who was new to reloading that used a charge bar minus the powder bushing .. with a bad result and another of a fellow who used Bullseye because he had been told it was usable in reloading shotshells; it is, for some target loads in the 12 ga. w/light shot charges. The gent in the story was using it for some heavy waterfowl loads in an amount way past stupid. I have no idea if those tales were true or not, but they both went around quite a bit some years ago.

I know of several 30-06 shooters that in seeking a downloaded cartridge, blew chambers. The case capacity and low volume of powder resulted in not a sqib load, but rather, complete detonation. Destroying the rifle.
Same can happen with a shotgun.

So, my belief is this.
Stick to published data.


I cringe when I read about handloaders toying with untested recipes.
As to mistakenly loading a shell or two with the wrong powder, What happens when you pop off the powder bottle and switch powders on a Mec? Is any left in the bar?

If there is, then both the variety, and quantity of powder could be wrong for the next shell.
I am not near my reloaders to see, so someone please see if this last idea is true.