Wondering ?????

[C.O.B.]

Originally Posted by Bruce Day

How do you know the shooter did not go to the RST tent 75 yards away and get a box of shells with exactly that load? Why would that not be the most likely scenario?

I highly doubt someone bought a box of RST just to shoot a gun a couple of times. More likely they had 16ga ammo and used that. It's not out of the realm that someone used 1 1/8th loads for shooting targets either.

I believe this gun is a #1 frame.

[Drew Hause]

"I don't think we can learn anything from this exercise."

Few more insightful words have been typed

HOWEVER, having participated in a number of barrel bulge/burst and shotgun blow-up discussions I'll babble anyway
I believe a 2 part barrel burst failure analysis and metallurgical study will appear in the DGJ Fall issue.
Lots of information, and scary pictures here, along with some anonymous sniping
http://www.shotgunworld.com/bbs/view...p?f=5&t=366087

1. A Parker Service and Proof Load table was published in the 1930s and reproduced in The Parker Story p. 515. 12g 2 3/4” shell Service Pressure is 10,500 psi. Definitive proof used 7.53 Drams (no doubt) black powder and 2 oz. shot with a pressure of 15,900 psi. The pressure was (likely) measured using LUP and modern transducer values would be 10-14% higher, or more than 17,500 psi. I am not aware of any definitive information as to turn-of-the-century Parker proof pressures.

2. Under the 1896 British Rules of Proof, 12g 2 1/2” and 2 5/8” chambers (bore .710-.740) maximum service load was of 3 1/4 Dram Eq. with 1 1/4 oz. shot.
https://books.google.com/books?id=in...AJ&pg=PA296&dq
Definitive Proof – 6 1/2 Drams Proof-House Black Powder with 1 2/3 oz. No. 6 shot = 10,100 psi + 10 - 14%
Supplementary Nitro Proof with 4 1/2 Drams of C&H No. 2 T.S. powder and 1 2/3 oz. shot = 16,400 psi + 10-14%

3. 16 bore British Service charge was 1 oz. 2 3/4 Dram Eq. = 38 gr. Bulk Nitro powder. Published pressures + 10-14%:
C&H No. 4 - 7,480; “Schultze” - 8,250 psi; “E.C.” - 8,960 psi
The U.S. 16g standard was 1 oz. with 2 1/2 Dr. Eq.; likely about 7500 psi with Bulk Powder by modern transducers

4. There are a number of bursting pressure formula; Burrard used the Alger Burst Formula:
Burst pressure = Ultimate tensile strength x 3(OD – ID) / OD + 2xID

There is also Lame, Boardman & Lame, American Standard, and Barlow's:
P=2 S t / D
P=Bursting pressure in psi.
S=Tensile strength of material in tube wall.
t=Wall thickness in inches.
D=Outside diameter in inches.

Barlow’s refers to a pipe capped at both ends with a static pressure (a pressure cylinder). Shotgun barrels are not designed to be pressure vessels as one end is open and the pressure rises and falls quickly. I've discussed this issue with a mechanical and a metallurgical engineer, and there is essentially NO formula that can be used for shotgun barrels. Nor can the Hoop Stress Formula be reliably applied.

NOTE: every formula requires knowledge of the tensile strength of the metal AND the wall thickness. Without that information any speculation is at best a guess.

Wallace H. Coxe, in "Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics" published by E.I. du Pont de Nemours & Co. in 1931 cites a study in which a fluid steel barrel was cut to 9” and capped, then a series of progressively increasing pressure loads fired. The barrel cap was blown off and barrel burst at 5,600 psi.

4. From Major Sir Gerald Burrard, The Modern Shotgun, "Volume 3, The Gun and The Cartridge", 1948:
“In the case of an obstructional burst the really essential evidence is the ring bulge. If there is a ring bulge, there must have been an obstruction…”
Odd to have obstructional bulges at the same place in both barrels, and Burrard also makes the point that "rib lifting" almost always occurs with ring bulges. which I do not see.

5. 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.

6. This is a 1902 16g No. 0 L.C. Smith with chambers extended to 2 7/8" with wall thickness at the end of the chamber of .096". Likely the victim of 16g "short magnum" shells with 1 1/4 oz shot



Radiography thereof



7. So what happened to these barrels?
My opinion, which is of no greater validity than anyone else's, is that this was NOT obstruction but inadequate wall thickness from previous honing.
"Mirror bores" in any vintage double should be huge red flags.

8. It might be relevant that some "low pressure" loads use powders with a slower burn rate, producing a lower peak pressure BUT slightly MORE pressure further down the barrel. Note the DuPont Oval curve below



Red Dot vs. PB (no longer available)

[Bruce Day]

Thanks Drew Your hypothesis of causation is the same as mine. Any load from RST, Remington, Winchester, Federal, Fiocci or Rio that could have been placed in the gun would certainly have been less than original proof pressures and likely less than max working pressure.

Honing sure does produce high condition beautiful barrels. Before anybody blames the shooter, the gun needs to be inspected.

[Paul Harm]

With normal wall thickness, the chambers blow with too high a pressure. The barrels past the chambers blow if there's a obstruction. With both barrels bulged in the same place I wouldn't think it's an obstruction, but thin barrels. I fully agree with Bruce and Drew.

[Joe Wood]

+3 for thin walls and most likely lengthened cones. I can't imagine a factory original one frame 16 not having enough meat to digest almost anything. And to happen in both barrels in the same place makes it almost a certainty in my mind.

Steve Barnett is one of the "good guys".

PS: I shoot a lot of damascus guns and consider all to be perfectly safe. However, a few months ago I got stuck with a GH 12 with 28" barrels that upon measuring the walls near the chambers am convinced they would be very dangerous to shoot even low pressure loads. I mean they are scary. Fortunately I have a set of widowed barrels that fit almost perfectly and are off to the smith for final fitting. I hate to destroy the original barrels so am trying to figure out how to mark, plug, or whatever the bad ones so they will never be fired. Any ideas?

[Jeff Higgins]

Originally Posted by Joe Wood

+3 for thin walls and most likely lengthened cones. I can't imagine a factory original one frame 16 not having enough meat to digest almost anything. And to happen in both barrels in the same place makes it almost a certainty in my mind.

Steve Barnett is one of the "good guys".

PS: I shoot a lot of damascus guns and consider all to be perfectly safe. However, a few months ago I got stuck with a GH 12 with 28" barrels that upon measuring the walls near the chambers am convinced they would be very dangerous to shoot even low pressure loads. I mean they are scary. Fortunately I have a set of widowed barrels that fit almost perfectly and are off to the smith for final fitting. I hate to destroy the original barrels so am trying to figure out how to mark, plug, or whatever the bad ones so they will never be fired. Any ideas?

Joe could those barrels be lined or perhaps shot with sub-gauge inserts?

[Fishtail]

The honed barrel theory is a good one...but it's still just a theory until we get some more complete data.

To counter, I'd offer that Steve Barnett would know they were thin and would not have had the gun out for open shoot day.

[C.O.B.]

I doubt we will get any additional data. I don't know if Steve checked the wall thickness prior to purchasing or trading for the gun. IF he knew it was thin the gun would have NEVER been on the table.

[Craig Budgeon]

To answer the question you asked. Minimum proof pressures in Austria for 16 ga. and above is 12,800PSI, for smaller gauges the minimum is 14233PSI. Proof loads manufactured by Remington produce pressures which exceed standard loads by as much as 50% and are clear plastic and marked as proof loads. Remember this when you remove a bulge from a barrel the bulge has already yielded once and removing the bulge forces the metal to yield again. Finally since I value my eyes above all my other senses I test Damascus guns I want to shoot by tying with the top rib against an 80 lbs. truck tire, adding 30 ft. of string to each trigger, lying face down on the ground with a hard hat, and pulling both strings one after the other. Yes I used proof loads and hunted the gun there after.

[GH-16]

After thinking about this some more. I've reminded myself of a personal experience I had with a CE grade Fox with 30" cromox fluid steel barrels.

I bought this gun when I was fairly new to older doubles and was still in the make the gun the way I want it to be phase. I didn't like the full & fuller chokes it came out of Philly with, so I sent it out to a well known double gunsmith to have them opened. I stressed that I didn't want them opened if the wall thickness didn't allow the procedure to be done. He supposedly measured them & we agreed to have him do the deed. When I got the gun back I took it out on a hunting trip in eastern Colorado. I forget the exact load I was shooting but they were a typical 6 shot pheasant load. "not one of these high power pheasant loads available today. A bird got up and I missed on the first shot, so I followed up with the second barrel.

My buddy that was with me immediately asked what I was shooting because it sounded funny. I started looking the gun over & found that both barrels had bulged at the lead to the choke tapers. Yes both barrels were bulged in the exact same spot shooting the same ammo! These shots were the first shells fired in the gun after the chokes were opened. Yep it only took one shot per barrel to bulge them.

I sent the gun back to the gunsmith and he immediately took the position that I was shooting too hot a load for the gun and wouldn't stand by his work. When I got the barrels back I had them measured for wall thickness. What we found was the walls at the start of the choke tapers were down to .010" where the bulges started. I've always felt that if I hadn't had the chokes opened that nice set of Fox barrel would still be bringing game to the table today.

I know it's a long story, but one I feel relevant to the theory of lengthened chambers. Live & learn !