doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Interesting article on Old Guns and Pressure

Jeff [JNW] says, "I think large shot weights and high velocity are much harder on old guns than moderate to high pressures."

And therein lies the conundrum, exactly what is 'moderate' from a pressure perspective? I'd personally have to say 7~8K psi in a 12ga. Go to the small gauges & I honestly don't know, but there are very few published loads for 20's that go below 9~10K psi. That makes RST a very valuable resource for those guns continued use.

High velocity and heavy charge weights both increase recoil and it's effect on old wood is cumulative and either can result in a stock failure. You'll get no argument from me on either of those counts.

OTOH, pressure is a factor too oft not understood w/people wanting to somehow factor it in with velocity which is wrong. Rather, it is a stressor that is independent of velocity whose effect is also cumulative and it affects weaker/older mild steels more so in terms of cyclic life than more modern alloyed steels w/higher pressure tolerance limits. Trying here to put it into layman's terms and likely failing at the effort, but high pressures in 'old guns' not designed for it nor made from materials that can withstand it are affected in the negative just as much as using heavy shot charges & high velocity loads even though the causal factors are not remotely related.

In my experience the people shooting old guns are interested in them, know and understand any risk.

Damascus or anything else is not the issue now, but people just being handed a handfull of random cartridges and shooting them out of their gun with out understanding the gun, the cartridge, or the loading.

You did very well at expressing it, Tracy. I agree with what you wrote and was considering trying to say it myself, but now I'm glad I didn't. You did a much better job than I would have.

SRH

Using the 2240 lb long ton 3 3/4 tons comes to 8400 lbs. Anyone want to explain where those extra 3,000 lbs came from when the pressure was given in PSI. It is also noted if you use the formula worked out by the British for converting crusher tons to PSI 3 3/4 tons converts to 11,480PSI. This formula was sated to not be "Exact" but close enough for a safe comparison. If that 1927 "Conversion" of tons to psi was merely a wild guess someone sure was doing some good guessing. Also "IF" all those loads stated from this era with pressures in the 11K+ range were in fact actual Crusher Pressures our ancestors weren't shooting shotshells through their old guns, they were shooting Hand Grenades. 5 tons = 11,200 lbs. 5 tons in crusher pressure would translate to something around 15�K PSI.

I do completely agree that in older data crusher pressures were very often stated simply as PSI so care has to be used in their interpretations.

I will also state the shells developed such as the "Super X" using more progressive burning powders did not raise pressures over the current heaviest available loadings. What they did was allow heavier shot charges, higher velocities (Or Both) while staying within an accepted max pressure level.

Compare these loads posted by Drew & note that all these loads are recommended in a 1913 Lefever Arms Co catalog as "Proper" in their 12 ga guns of over 7 lbs weight, except the one using Oval which of course was not then available
.
Coxe previously reported 3 1/2 Dram Eq. 1 1/4 oz. loads:
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite - 12,600 psi
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi

Good point, Stan--although those are foreign-made (Belgian) guns on which you can find a lot of information in the proofmarks that you won't find on American guns.

I'm not an autoloader guy, although I've owned 3 16ga A-5s: a Standard and 2 Sweeties. But all were factory 2 3/4". Isn't there some other modification that has to be made to those guns, other than just chamber lengthening, before they'll handled 2 3/4" shells? Ejection port issues, maybe??

Re pressure, Curtis states in his articles that the then-new, high speed shells "developed approximately 500 pounds greater breech pressure than the corresponding standard 12ga loadings." Note that this was written AFTER the advent of SAAMI (mid-20's), by which time the industry was attempting to get a grip on pressure, velocity, etc via standardization--which didn't exist to the same degree prior to WWI. "Normal 12ga pressure", at the time Curtis was writing (late 30's) is given as 9-10,000 psi (which would actually have been LUP, so more like 10-11,000 psi as measured by transducers).

"In a 1927 Western Cartridge Co. flyer "Super-X The Long Range Load" by Capt. Chas. Askins the 12g duck load is described as 38 1/2 grains or 3 1/2 dram (powder not specified but likely DuPont Oval) with a breech pressure of 3 3/4 tons or 11,480 psi."

Miller: I'm sorry for the confusion. Askins said only 3 3/4 tons; I calculated the 11,480 psi.



I still don't know how to interpret the 28 grains of Ballistite running 12,600 psi (by LUP). Add 1000 - 1500 for piezo numbers and we're close to proof loads. How could these ol' boys still have all their fingers!?!



tw:
"Rather, it is a stressor that is independent of velocity whose effect is also cumulative and it affects weaker/older mild steels more so in terms of cyclic life than more modern alloyed steels w/higher pressure tolerance limits."
In the ONE formal failure analysis that I financed, there was no evidence of low cycle fatigue.
From the report by Adam Haskins at METL http://metl.com/services/
"The fracture surface exhibited a mixture of ductile overload (plastic deformation with both tensile overload and shear) and transgranular cleavage, indicating a ductal failure mode with rapid failure. The cleavage failure appeared to form preferentially in the iron component. No evidence of fatigue failure was observed; there were no striations on the fracture surface."

I've submitted a 2 part article to DGJ, which also includes the analysis performed by 'Zircon' on the Sherman Bell fluid steel and Damascus blow ups. No decision as yet if it will be published.

Drew,

What I was trying to address with my remarks on pressure has nothing to do with a failure, catastrophic or otherwise, rather it speaks to the effect of long term use of improper [overly high pressure] loads in old guns. For example, I have held & examined minimally hundreds of older Damascus bbl'd. guns in my lifetime that were relegated to 'wall hanger' status because they had been 'shot loose'. All of the same guns I'm speaking of had their Damascus bbl's. still in tact even if dented, heavily corroded inside, ribs loose, hooks reattached, forearms wired on, stocks cracked/repaired, &c. Empirically, that suggests much better integrity than today's wives tales give them credit for & I'll leave it at that. Back to the pressure thing and the low tensile strength mild steels most, if not all, older double guns were made from, they get 'pounded' excessively when using high pressure rounds to use the vernacular and the result is the same thing as plastic deformation, if I'm not mistaken. Another descriptor that can be applied to low tensile strength mild steels is they tend to be more 'malleable' than high tensile strength alloyed steels, i.e. more readily deformed.

When we examine an older double gun, we have to realize that even if the frame was properly case hardened, that there is no guarantee that the hinge pin, the barrel lump or even the opening lever's spindle and bolting was ever hardened at all, possibly leaving those components subject to excessive pressure deformation, over time.

Best, tw

BTW, this is not intended as any form of rebuff should it read that way, rather another attempt at better clarity on my part.

Isn't there some other modification that has to be made to those guns, other than just chamber lengthening, before they'll handled 2 3/4" shells? Ejection port issues, maybe??

there were something like 6 modifications that had to occur for the longer shells to work properly. chamber, ejection port, and ejector and I can't recall the other 3. I've got Shirley's book and would have to look it up.

The Winchester Model 12 Skeet Gun wasn't introduced until 1934. Winchester began making their 16- and 20-gauge Model 12s for 2 3/4 inch shells in 1926. There was never a Model 12 Skeet Grade. From 1934 to 1964 it was the Model 12 Skeet Gun.

I initially edited my above post and took out the pressures I had put in and replaced the hard numbers with the term "moderate". I did this because we don't know exactly what pressures are proper for each individual old gun. I do shoot lower pressure loads in most of my guns because there is no reason to use a higher pressure with today's component choices. If pressure was a non-issue then we wouldn't have pressure limits. Too much velocity, mass of ejecta or pressure can all be deleterious and need to be considered. I see some people shooting high velocity and low to moderate pressure loads who think they aren't doing any damage to their gun because the pressure is under 10K psi. We have to remember that all of this is a balance and there is no free lunch.
Regards,
Jeff