A Friend’s Gun Exploded Today w/ RST Shell

[DSizemore]

It doesn’t take a total obstruction to cause extreme pressures. This guy is fortunate!

[Randy Roberts]

Yes, very lucky. There's an older trap shooter at our local club that I have watched for who knows how many years. He performs the same ritual every shot. Break gun open, remove spent shell, blow down barrel, hold gun up and look down barrel, reload. He does it on the sporting clays range as well. I have a new respect for him and his diligence now.

[Big D]

A friend had a Caesar Guerini blow up in the same barrel location. He also is left handed, and escaped with no damage except a bruised ego. He is a dentist, so a mangled hand would have been a real problem In his case, it was operator error. Dropped a 20 gauge shell into the left barrel, must have gotten distracted, and stuffed a 12 gauge shell in on top.

[Craig Budgeon]

If the left most axial shaft located in the receiver is .125" dia. then the exploded cross section would appear to be between .040-.050". If that shaft is smaller the cross section would be closer to .040". Either way that's very thin that close to the breech, much to thin for my eyes!

[TxHuntermn]

Originally Posted by Craig Budgeon

If the left most axial shaft located in the receiver is .125" dia. then the exploded cross section would appear to be between .040-.050". If that shaft is smaller the cross section would be closer to .040". Either way that's very thin that close to the breech, much to thin for my eyes!

How do,we know,those dimensions??.

[Drew Hause]

I don't understand Craig.
The OPs burst is at about 9" and .040" is generally recognized as adequate wall thickness for fluid steel at that point.
The Smith Ideal chamber burst occurred where MWT at the end of the 12g chamber is usually at least .110". I did not however have the opportunity to measure that specific gun.

Another overpressure chamber blow out courtesy of David Trevallion



Likely 20g in front of 12g blow out



As said, bursts can occur with much less than total bore obstruction. A study by the Royal Military College of Science, sponsored by the Birmingham Proof House and the British Association for Shooting and Conservation, showed that an obstruction by 2 fibre wads (total weight of 4 grams) was sufficient to bulge or burst a 12 gauge barrel shooting a 28 gram (slightly less than 1 ounce) load. Peak pressure occurred 22mm (.866”) past the leading edge of the obstruction.

[todd allen]

Stuff happens in a hurry, inside a gun barrel!

[Craig Budgeon]

Mark, I have disassembled at least 30 English boxlocks in my lifetime and never has that shaft exceeded 1/8" dia. My vocation was a master instrument maker for the Eastman Kodak Co. fabricating precision sheet metal parts and machined parts. My hobbies include gunsmithing and participating in the Indianapolis 500 as assistant chief mechanic. My home provides space for a complete machine shop. I've been a machinist for fifty years

[TxHuntermn]

Originally Posted by Craig Budgeon

Mark, I have disassembled at least 30 English boxlocks in my lifetime and never has that shaft exceeded 1/8" dia. My vocation was a master instrument maker for the Eastman Kodak Co. fabricating precision sheet metal parts and machined parts. My hobbies include gunsmithing and participating in the Indianapolis 500 as assistant chief mechanic. My home provides space for a complete machine shop. I've been a machinist for fifty years

Thank you for the explaination. So, if “eyeballing” is allowed, to my eye, all three of the barrel failures that Drew evidenced have wall thickness that “looks” thinner than the subject gun.

[Craig Budgeon]

Drew, since the barrel flats on an English boxlock never exceed 4" in length its difficult to see how you chose 9" as the beginning of the explosion when it is no farther away than 6" from the breech. Just because I could, I went into my shop, pisked up a pair of Verney Carron barrels measured the wall thickness and would you believe that the wall thickness measured .068" 6" from the breech. Finally Drew when it comes to my safety I prefer my evaluation over yours.