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

Drew, I would ask the shooter if he ever checks the weight of the powder charge or does he just depend on the bushing chart. If he has not been checking weight of the thrown charge periodically you might have him run his reloader and collect a few samples. I know that I can influence the charge weight thrown on my reloaders by how I handle the equipment. I typically go down a bushing size to prevent heavier than desired charges on the single stage reloaders.

Drew thanks. Mec bars are known to throw light shot drops and depending on the size and antimony that would be about right and would only take a few pellets to make 1 oz.

The powder is .4 grs apart and if the LUP conversion is close to PSI that would be close to SAMMI.

The hull diameter of .821 behind the rim is greatly enlarged, and unless the chamber opening was that large the only way it could get that size is if the gun opened when fired.

Wasn't it Bromide?.In the tea, in England I believe.
That seems like a high psi load for an old Damascus gun,dontcha think?
Perhaps there was an 18+ grainer in the mix with the 17.4,17.6 & 17.8 's...those loads are pushing 10,000 ish,aren't they?.. though hard to tell with LUP
I don't load LUP recipes.They seem hot, never mind with a double tap of powder
franc

Saltpeter Franc - potassium nitrate
http://www.snopes.com/military/saltpeter.asp

Drew, I had to look see.... Bromide
franc

Thanks Franc.


Lots of news, but I still need to measure wall thickness of everything I can get to at the rupture.

The first spot where I can measure the bore is at 3 1/4" and is .750, then 3 1/2" .737, and 3 3/4" .733 where it remains uniformly until the choke constriction starts at 3" from the muzzle. Clearly the barrel expanded as it ruptured, but not like this



The first place I could use the wall thickness gauge was at 4" and it was .112, about the same as the end of the right chamber. At 5" .096 and 9" .060.
9" from the muzzle .039 and MWT was .037 at 5".

After serious cleaning, all the rust came off easily and the bore is without significant pitting.

Will get more pics up, and STILL trying to get a better pic of the extractor indentation on the steel head.

Bottom line: I think the barrel is still at factory specs and we can't blame thin anything, but again will report the wall measurements around the rupture tomorrow.

Drew, great detective work. All of your readings look good. We know the chambers of an L.C. Smith, but it would be nice to know the taper dimensions of this gun with 27/8" chambers.

If I'm not mistaken, potassium nitrate is also used for Nitre Bluing and stump removal (quick acting rotting agent)

David: the chambers are 2 5/8" as expected, with a short forcing cone

Amazing how much better pics turn out with a bright but slightly overcast day







This sure looks like a bulge? I still need to check all the empties for missing parts

Excellent photos, Drew!

With kind regards,
Jani

I was reading Drew's initial work and thought about the 737 Aloha Airlines plane that landed with the front third of the top of the fuselage ripped open---was traced to corrosion and the fact that each time the plane takes off and lands the fuselage is stretched open and closed. This slight movement over time "work hardens" the metal and makes it brittle. I would guess that a shotgun is the same way--each time it is fired the barrel gets a hoop stress as the metal tries to expand. That might be significant in an old barrel