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Pretty sure anything B&P is a CIP load, Stan. Anything CIP is going to be more consistent on pressure, and OK to use in any gun that remains in proof, even twist or Damascus. SAAMI, not so much. It will be at or under SAAMI max. That is about all you will know. That is by design, by the way. It give the manufacturers great leeway in how and what they use to load ammunition.

I agree with your number for old guns, but, I suspect that getting that number, consistently, with factory loaded ammunition that makes no claim to being anything but SAAMI compliant is a tough thing to do. The boutique ammo guys can and do make it. But, expecting to get it off a shelf at the local mart from run to run is perhaps a bridge too far, even with testing a few from time to time.

My oldest gun has steel barrels with .060 wall, 9” from the breech. I was always suspect of thin walls, but, it was more of a worry of denting them, for me. Somebody right here posted the results of testing on about half a dozen, older, 20 gauge factory promo loads that were right up against SAAMI max a few seasons past. That, was sobering to me, and, changed how I think about old doubles and ammunition. Pressure is the bugaboo.

Be well, Stan.

Best,
Ted

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Ted, that barrel looks like something was lodged in the bore, not high pressure. High pressure loads have the chamber opened up, not the bore. Now, if the reason for your post was to show a gun with very thin walls, that's a little different. But then who in their right mind would shoot a gun with .018 barrel wall thickness 9" from the breech ? That's not a over pressure question, but one of sanity.

Last edited by Paul Harm; 06/27/22 10:54 AM.
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Originally Posted by Paul Harm
Ted, that barrel looks like something was lodged in the bore, not high pressure. High pressure loads have the chamber opened up, not the bore. Now, if the reason for your post was to show a gun with very thin walls, that's a little different. But then who in their right mind would shoot a gun with .018 barrel wall thickness 9" from the breech ? That's not a over pressure question, but one of sanity.

There exist English 12 bore guns proofed at .018 wall. If the correct ammunition is used, no big deal. Unless you are me, and bang the thing into a tree taking a leak in the woods.

A man has just got to know his limitations.

I posted the blown up American gun as it doesn’t seem to have excessive wall thickness.

Best,
Ted

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Do you have first hand knowledge of the reason it blew up ? I've always been lead to believe that a gun blown up in the chamber is from over pressure, one blown up down the barrel is an obstruction in the barrel. I'm not trying to start an argument, but just thought a gun blown up from an obstruction maybe shouldn't be shown in a discussion about over pressures.

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Thin barrels do split

Perazzi MX2000 inexpertly "backbored" to a wall thickness of .012"

[Linked Image from photos.smugmug.com]

Honed to .739" with resultant wall thickness .018". I do not know the load which caused the split

[Linked Image from photos.smugmug.com]

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I’ll bet that was exciting.


“When faith is lost, when honor dies, the man is dead” - John Greenleaf Whittier
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Not as exciting as this Tom. 1st shot with 12g 2 3/4" Bismuth Magnum Game Load 1 3/8 oz. Unfortunately, I don't have the wall thickness measurements or the pressure of that load

[Linked Image from photos.smugmug.com]

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I shoot doubles with walls as thin as .018-.020 on a fairly regular basis. I am very strict about what loads I use and keep the pressures down to sane levels, 8,000 psi for 20 and 5,000-6,500 psi for 12's. The important thing to know is where are they thin and what your real pressure is on the load you want to use. Barrels at .020 are more likely to dent than blow up with sane loads. Thin barrels 20" from the breach do not scare me but anything less than that or closer than tat will need careful consideration before I shoot them. Very careful.

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Preacher, why do you post stuff like this???

Originally Posted by Drew Hause
Thin barrels do split

Honed to .739" with resultant wall thickness .018". I do not know the load which caused the split

[Linked Image from photos.smugmug.com]

And you also post stuff like this below, concerning your one-and only Damascus barreled OE Grade L.C. Smith 16 gauge gun...

Originally Posted by Drew Hause
"I personally measured the wall thickness of a 1906 L.C. Smith 16g No. 0E with “Good Two Rod” Damascus at .016”, 14” from the breech which [prior to having the wall thickness measured] had survived 250 2 1/2” 7/8 oz. Polywad Spred-R shells, 100 2 1/2” 7/8 oz. at 1145 fps. (about 8000 psi) loads [William Larkin Moore's], and 2 cases (500 shells) of 2 1/2” RST 3/4 oz. at 1100 fps (4,600 psi per RST) without rupture or dimensional changes."

My 3/4 oz handloads are listed in the manual at 5400 psi, a buddy chronographed the load at 1185 fps, and cases of that load have been through the gun.

The end-of-chamber MWT is .114" R (the thin barrel) and .118" L. 9" from breech is .032" R and .044" L.

It is my opinion that barrels that are thin from 12" from the breech to the muzzle (where pressures are much lower) are likely to split; not disintegrate



But the hand guard provides some additional safety.

You can get pissed at me for pointing out the obvious, and I'm sure you will be blinded by personal animus in your response. But it sounds like KYJon feels the essentially same way about guns like your one-and-only Damascus barreled OE Grade L.C. Smith. And he was commenting about barrels that are not only thicker than yours, but also have that .018" to .020" wall thickness a full 6" further from the breech than your gun.

Originally Posted by KY Jon
Thin barrels 20" from the breach do not scare me but anything less than that or closer than that will need careful consideration before I shoot them. Very careful.

It is little wonder that your friend Ed is repeatedly questioning everyone about what barrel wall thicknesses they consider safe, and why they feel that way. Nobody here, who has any good sense whatsoever, would advise someone to buy or shoot a ratty old Damascus L.C. Smith O Grade that has barrels with an .016" wall thickness at 14" from the breech. If you really wish to pass yourself off as a copy-and-paste internet shotgun barrel expert, then you really need to stop posting flawed and conflicting data, and potentially dangerous advise.


A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.

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Originally Posted by Paul Harm
Do you have first hand knowledge of the reason it blew up ? I've always been lead to believe that a gun blown up in the chamber is from over pressure, one blown up down the barrel is an obstruction in the barrel. I'm not trying to start an argument, but just thought a gun blown up from an obstruction maybe shouldn't be shown in a discussion about over pressures.

That would be only two reasons barrels ever blow up, and it would leave out barrels honed too thin, and loads too hot used in those thin tubes. I also saw a Darne that had a crease dent in the barrel, that the GI importer tried to remove with a Peter’s high brass load that resulted in a very neat split exactly where the crease was. Undented, the Darne would have been up to any factory 16 gauge load the fool could have stuffed into it.

Best,
Ted

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