doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2.75" shells in 2.5" chambers

Miller, I believe I sent you--or someone else on this BB who requested it--a copy of the chapter from Thomas' book in which he addresses the above subject. To summarize, the experiment in question--by IMI--involved "nine experienced shots of various build, shooting under a wide variety of conditions with guns of different types, weight and boring. The cartridges were all loaded to give the same velocity to the same shot charge, though by means of powders of various rates of burning. The shooters did not know what they were firing, but were merely required to give marks for recoil. They were unanimous in assigning the lowest recoil to the cartridges loaded with the fastest-burning powder, the dynamical effect of which was checked throughout by electric accelerometers built into the stocks of the guns, and their conclusions have since been widely confirmed."

Since no particular brand of cartridge (nor powder) is mentioned in the text, that would seem to remove any potential "bias" from the experiment. That is, the company trying to prove that THEIR shell (or powder) recoils less than the competition. Besides which, if the company in question makes various types of shells and powders, what advantage is there in promoting one of their own shells (or powders) over another of their own shells or powders?

I did not read the test referred to. I had a book by Thomas, for a while, that seemed to me to be so full of crap that I did not keep it as a reference. I think it was titled Shotgun Facts, even though it didn't contain many, IMO.
However, as quoted, the test above says to me that the faster burning powder produced less true recoil(which was also felt) because there was less of it needed. Right in line with the standard, long accepted formula.
I do remember a similar test in probably Guns and Ammo, some years ago. The conclusion in that test was that the shooters could not detect which shells were loaded with fast burning powder and which contained slow powder. Easy for me to believe, also, as the time difference in the pressure peak betwwen the slowest to the fastest is very tiny.
Still have no idea what Raimey is talking about. No offense, maybe I'm just too iggerant to follow it.

In spite of the fact that a lot of information has been put forth concerning recoil, the original post was:

Answers should be forthcoming.

JC

Not to get into the Do some notice a push more than a whack (the "Get It Over With" G T Thomas school of pain thresholds)?; the pressure biz can be stated two ways. A relatively more inertial load (read more shot) "needs" a relatively slow powder to prevent pressure spiking too high before the load gets moving and to maintain pressure over the time necessary to defeat inertia. The relatively less inertial load (less shot) "needs" the faster igniting powder to avoid outrunning the burn rate over time, increasing the volume which gas must fill, and thereby decreasing pressurization (and efficient burn). The other way of saying the same is that the fast or slow powder needs its appropriate shot charge as a blowout plug in the vessel of reaction. Expanding gas is sure necessary to do the work, transfer energy, or whatever, but where is there shown to be a direct correlation between small-p pressure and velocity in Newtonian mechanics. Others besides Thomas are "hooked on a feeling".

jack

Well, Mark, the answer to your question, "can I shoot 2 3/4" cartridges in a short chamber?" seems to have been answered! First memorize the SAAMI report, then fire your gun remotely while its hanging from a rope, get a degree in physics and mechanical engineering, buy some gauges to test stress, send your loads off to an independent lab to have them evaluated, then fire it from the space shuttle, with the tailgate down, and most important DONT listen to any one who who cant confound you with equations and datums...You are on your own, Pal, I got lost a long time ago...

Larry;
The info I received from you on this was essentially useless. Reason "NO" data was included as to what the test loads themselves consisted of. No mention as to what type of powders were tested. As you have never given any particulars I am asuming you have none. Since Thomas did not state any I also assume either he did not have them, OR didn't want to include them. Now it is a well known & established "Fact", Measurably So, that the progression of shotshells from Black, to Bulk Smokeless, to Dense Smokeless have each resulted in a reduction of Recoil. A 3 Dram charge of BP weighs 82 grains. A 3 Dram "Measure" of bulk Smokeless such as Schultz or DuPont Shotgun weighs 42 grains. A charge of Dense Smokeless equivelent to 3 Drams of BP such as Sporting Ballistite or Infallible weighed 24 grains. These differences in weights are significant enough to make a discernable difference in recoil. Thomas' reasoning on this subject, IE, that the fast powder loads had less felt recoil because It occured so fast the shooter did not have time to think about it, while with the slower powder it was of longer duration so the shooter noticed it more, is about as "Patently Absurd" as saying it's OK to lay your thumb atop the nail head as an aiming point "IF" you "Hit it Fast Enough".
As it stands right now it seems virtually everyone with an opinion on this subject, Except; You, Mr Legg & Myself think one can go to a slower powder & reduce felt recoil. You on the other hand, in your blind devotion to the words of Thomas, without in the words of Mr Bell "Finding Out for Yourself" apparently think one can switch to a faster powder & reduce felt recoil (If you didn't say that, you have said Nothing).
Mr Legg & Myself take the opinion that unless either total weight of ejecta or speed of that ejection takes place no significant change in recoil will be felt.
I Guess everyone will just have to believe whatever they choose to.
To answer the original question;
IF the longer shell were loaded with a load appropriate to the gun & if the loaded shell had clearence past its crimped end in the chamber, I would not concern myself that the end of the fired hull, after the opening of the crimp, lapped up into the cone a bit. I would expect no significant change in either pressure, velocity or recoil. If the length of the loaded shell were enough longer than the chamber that it protruded into the cone before firing, I would refrain from firing it in that gun.

Miller, your last paragraph, I believe, is the best answer and the one that most of us can agree with. Thanks...

LOL!! Too funny. I tested some 2.5" loads with my Lefever yesterday for the first time. After signing my last will and testament, I kissed my wife, petted my dog, tied a string to the trigger, crawled down into my bomb shelter and let er rip. Ok, not really, but shockingly, the twist damascus barrels didn't blow up (Amazing. I guess I'm not the only one to have fired the gun in the last 100 years), they all went bang, some patterned better than others, and some kicked a bit more than others. It was all very scientific, until I got yelled at for using the patterning board when the range was closed. Oops. I thought that was ok, but obviously not.

In all seriousness, one thing that did surprise me was how little difference there was in loads where I used a full plastic wad and ones where I cut the petals off. Pretty negligible difference. That Lefever throws a very tight pattern too, choked m/f. Time to break out the spreader loads, publish my all findings, and send them off to Ithaca.

Miller, I realize that Thomas was a gun writer; therefore, in your opinion, of low credibility--unless he happens to agree with you, which would make him one smart guy. However, he was also an engineer, and I think on this subject, his credentials are at least as good as yours--whatever yours may be.

What Thomas does not state, at least not with total clarity, is whether the shells loaded with the faster burning powder had a lighter powder charge than the ones with slower burning powder. That, of course, would explain why they recoil less. He does specify that the shot charge and velocity were the same, and since he was an engineer--although I don't like to assume--I think it's likely a safe assumption that he realized that a lighter powder charge of faster burning powder, producing the same velocity as a heavier powder charge of slower burning powder, would automatically mean reduced recoil. That puts us back at his conclusion that ALL THINGS BEING EQUAL--same weight of ejecta, including powder, and same velocity--the faster burning powder will reduce recoil.

I don't know if he's right or not. Perhaps time to turn that one over to Mr. Bell as far as measurable recoil goes. Felt recoil . . . well, some people are skeptics when it comes to anything that can't be measured. Except, perhaps, the existence of God.

To return to the original question, I'd say it's highly unlikely that 2 3/4" shells, reloaded to 7,000 psi, would be dangerous in a Lefever chambered at 2 1/2". Pressure might increase slightly, per Bell's experiments. Recoil might also increase if the gun has especially short and sharply tapered forcing cones--in which case one might not want to use the longer shells in that PARTICULAR shorter chambered gun. Or else lengthen the cones.

Hi Larry,
You were doing fine until you got to the forcing cones. Forcing cones have an effect on recoil because________________________?