doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Disaster struck yesterday

DeltaBoy; A long bbl split like that looks more like a flaw in the steel, that was drawn into a seam in man'f. Most likely over time it finally decided to let go, for no apparent reason, most likely fatique from use. Bbls burst from an obstruction will most always show a ring bulge. I do not see this on this bbl. Don't blame your son, he most likely was in no way responsible.

I questioned the seller about the fox pictured. He claimed it let go while shooting factory #4 hunting loads. A short time later, another one showed up on eBay. Same crack on the opposite side of the frame. That seller never responded to my questions.

Interesting that yours cracked the same way. I am very glad you were not injured.

I've had 1 gun re-cased. John Griffin at Classic Guns was very though in questioning me regarding the gun's history. In particular he wanted to know if the gun had ever been re-cased since it left the factory. I am not sure every one with a furnace and quenching tank asks that question. He warned me that a gun can only be subjected to this process so many times before damage is done. Either the metal will warp or become brittle. It is very difficult to know the full history of a 70-90 year old gun.

Interesting that you say the gun was refinished. Was it re-cased? Who did the job? Not that they are to blame in any way.

Pete

Interesting diagnosis, Jones. The location of the hammer axle directly in the plane of heavy bending forces is frequently mentioned as a potential point of failure in boxlocks but the searchlight has always been on the crack itself. I've never heard this scenario in which a gun not previously known to double does so as a result of dislocation of the sear axle contingent to cracking the bar and opening up the bearing points, a sequence of causation which would not occur to most of us particularly when a gun comes apart in our hands.

I'm puzzled by the photo of the Ebay Sterlingworth. My assumption has always been that when you pull the triggerplate on a Fox, you're looking at a single piece of steel with only the hammers, sears, cocking rods, lever, bolt and safety bits added. When I look in the crack in the photo, I see another uninterrupted wall of steel underneath as if the construction were laminar and the bar only a very thin shell in this area. What am I missing?

jack

DeltaBoy, 2piper is right (as usual). Relatively "minor" bore obstructions (and I hate to imply ANY obstruction is not very serious) will cause bulges. As increasingly severe obstructions are tested, they create increasingly larger bulges, then ruptures. Obstruction ruptures usually are local blow-outs rather than splits.

Greener in "The Gun" illustrates bulges created by light wad obstructions, pictured next to a blow-out caused by two light wads with just a small fraction of shot between them.

Should have said hammer axle in above post. Sorry, but I can't find the edit function on the quick reply.

jack

2piper, Fred, An Elsie with a barrel flaw? But this explantation makes me worry about the other barrel. This happened about 25 years ago and I just found someone to fix it. The wonders of the internet.

Larry et al: I am not clear on the difference between "ReCase Coloring" and "ReCase Hardening". Is it just a matter of degree (and degrees--heat) of doing the same thing? I tend to refer to screws as needing case hardening (for a practical reason) and receivers as being case colored (mostly for asthetics). Thanks, Gil Russell

Deltaboy, I too have great respect for LC Smiths. My main point was/is that I see no signs of an obstruction having caused your bbl split.

The vintage barrel materials project now underway will be analyzing another bbl, with a very similar and similarly-long split. Coincidentally, it also is from an LCS. It hasn't been analyzed yet, but certainly will be.

What caused that failure, or yours? I don't know yet, but can identify several possibilities.

Flaws do happen, even in the best products, and have a number of origins. Slag inclusions and voids were common in vintage steels. Homogeneous ("fluid") steel barrels were made several ways. Some of these drew the metal out considerably, in the longitudinal direction. This provided grain orientation and also tended to elongate inclusions and/or voids. Proof testing found the worst ones, but some undoubtedly survived proof.

Another possible cause or contributor is wall thickness insufficient for the local gas pressure. Locally-thin walls can be due to excessive striking (filing) on the outside, or boring out inside. Either can be done after the gun leaves the factory, to whatever brand and quality of gun. Of course, any local strength issue is exascerbated, increasingly, as local gas pressure is increased if higher-pressure loads are used.

One other common problem is a stress concentrator, which has a local weakening effect similar to a "flaw's." One good example illustrating this (or actually illustrating avoiding it), on well-made guns, is the rounding of the inside corner at the junction of the water table and standing breech. A square corner would suffer much higher stress for the same applied forces, than does a corner having an effective radius.

A longitudinal groove in a barrel wall multiplies the otherwise-uniform hoop stress, at its location. The exact effect depends on the geometry of the groove, the material hardness / lack of ductility. The perfect example is the effect created by a glass cutter. If memory serves, such a scratch in glass can raise bending stress by a factor of several hundred, at its location.

Engineers didn't understand until the 1930s that cyclic stress above a threshold value, but far below the yield point causes cumulative damage. This problem is magnified, often greatly, by seemingly-innocuous ornamentation that causes dangerous stress concentration. In one case photo-documented in a classic fatigue study, text stamped in a flat-bottomed font, closely-spaced, created high local stress that caused an airplane propeller to break with fatal results. (I don't have a photo posting site, but will be happy to forward a copy of this failure if anyone wants to post it.)

Fred:

Have also seen an LC with the longitudinal barrel rip in a Roanoke VA gunshop.

jack

One poster mentioned the "chicken-egg" situation which is the most likely. Further, every time I blow up a shotgun, I take every remaining shell in my bag, cut them open one by one, and examine and weigh the contents, actually examine everything and weigh the powder. How did your remaining ammo come out on the scale?? Second question, how much of a coincidence is it that the receiver was just run through an oven? Who is your case harderning guru? Not that he is at fault, but that is one factor that should be thrown into the mix.