Parker Gun Collectors Association Forums - A Friend’s Gun Exploded Today w/ RST Shell

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"An over-charge would not cause that kind of burst that far from the chamber."

I agree with Dean.
THIS would be a (very) over-charge blow out

http://pic20.picturetrail.com:80/VOL.../413805715.jpg

Quote:

Originally Posted by Mark Ray (Post 260703)

It amazes me that he did not have a severe injury to his left hand....must have been wearing gloves at a minimum! Had a friend years ago have a similar explosion, finally figured out that his "old fashioned" oil mop that hooked on to the end of the rod to pull through the barrels had unhooked itself in the bore, and he got distracted between that and putting the gun up with the mop in the bore. He figured it out when he found the mop missing from his kit. My friend got some permanent black freckles in his left ear and cheek, and donated half a pinky finger.

Also luckily he's left handed

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.

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!

Quote:

Originally Posted by Craig Budgeon (Post 260742)

How do,we know,those dimensions??.

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

http://pic20.picturetrail.com:80/VOL.../284440656.jpg

Likely 20g in front of 12g blow out

http://pic20.picturetrail.com:80/VOL.../405843826.jpg

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.

Stuff happens in a hurry, inside a gun barrel!

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

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.

My apologies for being obtuse, but where is the "axial shaft" located in the receiver?