doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Blow Up Post-Mortem Part 2

Thanks

Image of both primers, and comparing the two visually, the blow-out shell primer is slightly proud of the plane of the bottom of the shell, and the copper component slightly bulged



I will measure the shell head as Joe suggested. In this image the left shell is slightly raised from the chamber.

Drew,

I strongly question the appearance of that primer. It looks like classic cratering to me, and flattening at the edges, a sign of high pressure. I've seen this many times when working up max loads for a rifle.

SRH

What Stan said.

+1 to Stan on the primer

So the load is a grain away from modern proof limits. Not much room for errors.

Stan is dead on. It appears the copper began to flow backwards around the firing pin. Clearly over pressure regardless of the age of the gun.

Pete

I find the pic of the hull from the failed bbl. most interesting. It would appear that the cleaner green area w/the jagged tear was in solid contact w/the chamber wall at the time of failure & the 'less green' or 'frosted' portion was subject to burning powder gases [blow back?]. I would find that consistent w/Joe's observation of an expanded head at the uppermost head's [or 'brass'] edge. The fact that the torn area or 'clean green' outer portion of the hull does not show any signs of escaping powder gases is perplexing.

FWIW, I recently fired a 20 ga. Remington G.C. hull [previously several times reloaded] in a 12 ga. gun. It was NOT intentional. I have retained that fired hull. There are some similarities to the hull's outer appearance. My fired 20ga. Remington C.G. hull clearly has an expanded edge at the top of the head and also exhibits similarities in it's outer hull surface being 'frosted' in appearance and the mouth being split in several areas and clearly 'brittle'. I consider myself both lucky and fortunate that the Remington hull was sufficiently strong & well engineered to have withstood my stupidity; error, if you wanna be polite.

Is the chamber's dimension oversized toward the breech end? Could some earlier pits or corrosion have been removed from excessive honing? Just questions.

I have to ask myself if what we are looking at in this particular instance is not the result of an unsized hull minus the head from a previous round stuck in front of the fired round? That reads awkward at best. Said another way, if the previously fired reloaded round was previously fired in a substantively oversized chamber & not resized, could the metal head been ejected alone and the body of the hull become lodged directly in front of the fired round? Could it have been a loaded 20 w/the head still attached? Again, it is but another coupla questions.

First, thanks for the leg work and passion on this situation. Nothing but good can come from this.

I hesitate to add to what's been said, but agree the fired primer is definitely a clear clue to what's happened.

I'll add another thanks Doc Drew for following up.

I may be seeing it wrong, but I believe the fired primer on the right hand side of the pictures shows possible signs of higher pressure than the left blown side. I think that gun has been eating a steady diet of over pressure loads for some reason or another. If all the right components are there, maybe you'll find a bushing throwing a heavy charge.

If a dimension of the gun is causing the pressure signs, you may find similar in the other barrel. I'd still guess that barrel integrity could be questioned , and you may find signs of a bulge. I don't think the red rust has anything to do with this mishap, but I think there're signs of black oxidation or defects that might be preexisting from before the barrel let go.

If they're willing to chat about it, maybe ask the metallurgist why the grain of the steel on these failures seems to be very coarse. Please also pass along thanks to the shooter/owner. Interested to read what you come up with when those reloads come apart. Take care.

Joe Wood and Stan are both correct about the suspicious appearance of the primers. I don't really know how the thickness and hardness of shotshell primer cups compare to rifle primers, so I don't know if valid comparisons can be made. But the sharp edge and seeming extrusion of primer cup material around the firing pin on the blown shell tell me this load, whatever it was, probably exceeded safe limits. I'd sure at least try to get my hands on all of the shells that were used from that particular box that day to measure and check for missing base wads, etc. I know that will depend on whether the shooter picked up all his empties, and what was done with them in the excitement of the aftermath. Thanks for continuing to share. You may never find the true cause, but it's important to at least try.