Wondering ?????

[Dean Romig]

There's a LOT more to this story that we will probably never know. I don't think we can learn anything from this exercise.





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[Bruce Day]

The current SAAMI maximum pressure for a 16ga 2 3/4" cartridge is 11,500psi regardless of shot and powder loading. At 80 percent of proof pressure, this requires minimum SAAMI compliant proof of 15,365 psi for a 16 ga gun, manufacturers may exceed the minimum standard .

Current production cartridges may be at or below the 11,500 pressure, particularly 1 1/8 loads.

At the time the Parker in question was made, the normal max pressure for 16 cartridge was 10,200 if I recall correctly, this gives a minimum proof load of 12,700 that the gun would have been tested with.

Tests have shown that chambers 1/4 " short increase pressure over nominal 2 3/4 by about 5 percent. Therefore assuming it was short by 1/4 " ( which may or may not be true) , a possible pressure could have been 11,500 plus 575, 12,075.

Therefore, the maximum pressure that factory shells loaded to maximum SAAMI specifications would have provided exceeds the load pressures the gun was intended for but remains less than what the gun was proofed with. The few tests done and reported in DGJ have demonstrated that the tested composite steel barreled guns withstood at least 4000 to 5000 psi above proof before they experienced non elastic deformation.

Neither the bore ID nor wall thickness has been disclosed for the gun in question. That information is critical to any informed analysis. O framed 16's , which this may or may not be , often do not have much wall thickness to spare.

[Bruce Day]

We saw a fairly new Italian over under rupture forward of the chambers at the Southern about ten years ago. He was using Winchester trap handicap gold loads that would have been loaded to SAAMI max.

I have an acquaintance who had a Guerini rupture halfway down with factory handicap loads. He saw the shot cup fly out on the previous shot so it was not a squib and stuck wad issue. He later had the barrels measured, bore ID was standard but the wall thickness was less than .020, how far less I don't recall but they were made surprisingly thin.

[Fishtail]

It's possible that the offender didn't even know the barrels had swelled. I could easily see myself shooting a gun at an event where there were lots of people and commotion and never paying that much attention to the gun. Keep in mind the swells are just that - gentle swells - and not ruptures or jagged edged. The Damascus pattern helps hide them, too.


I'm not taking sides....but I gotta say whenever I let someone shoot one of my guns I am very specific about what shells they use. Very specific.

It appeals to the ego to be a laid-back gun dealer who jauntily hands someone a multi-thousand dollar, 100 year old gun while casually saying "Bring it back when you're done..." But I think the dealer in this case has learned a lesson the hard way and will be less magnanimous from here on out.

"Don't lend someone your car or your girl...someone might throw a rod in 'em."

[Dean Romig]

Originally Posted by greg conomos

I'm not taking sides....but I gotta say whenever I let someone shoot one of my guns I am very specific about what shells they use. Very specific.

Whenever I let someone shoot one of mine, not only will I insist on what shells they will use - I will hand them a box or two of MY shells.





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[edgarspencer]

Originally Posted by greg conomos

I'm not taking sides....but I gotta say whenever I let someone shoot one of my guns I am very specific about what shells they use. Very specific.

It appeals to the ego to be a laid-back gun dealer who jauntily hands someone a multi-thousand dollar, 100 year old gun while casually saying "Bring it back when you're done..." But I think the dealer in this case has learned a lesson the hard way and will be less magnanimous from here on out.

Couldn't agree more

[Bruce Day]

All the commonly available factory loaded 1 oz 16ga cartridges I am aware of generate chamber pressures below 10,200, or the design max working load for the gun. 1 1/8 loads are over that to the full current limit of 11,500. It seems implausible that a person would come to shoot targets with 1 1/8 oz 16 ga loads.

We have yet to be told the bore or wall thickness of the bulged barrel gun.

At the time this G grade 16 Parker was made, the Parker recommended load was 7/8oz at 2 1/2 drams. 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?

[B. Dudley]

Originally Posted by Dean Romig

Whenever I let someone shoot one of mine, not only will I insist on what shells they will use - I will hand them a box or two of MY shells.

Very true. That way if something goes wrong, you have no one to blame but yourself. At least you know what shells are being used and if you reloaded them, then you know who may have made the mistake.

[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)