doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2 3/4" in a 2 1/2" Chamber

JDW,

(JDW:)As to the statement made by vh20, I was the one that gave the statement of using a 3" shell in a 2 3/4" chambered gun as a comparison of 2 1/2" to 2 3/4". Nowhere did I state that it was low pressure, it was just an analogy of using a longer shell in a shorter chamber.

No, of course you didn't, and I didn't say that you did. I'm not sure what you mean by that, it wouldn't have made sense. My point was that it is NOT the same BECAUSE there are no 3" low pressure shells manufactured anymore (although there used to be). You didn't mention ANYTHING about pressure, and that is where my disagreement came from. We don't stick 3" shells in 2-3/4" guns because they are magnums, and unless we know the pressure, we EXPECT it to be very high (same with the 2-3/4" magnums you mentioned). I can find some 3" loads in the manuals that are close to being low enough for my comfort, but not quite. Then we expect we are going to add another 10 or 15% more pressure to that because of the mismatched length. In other words, your analogy violated the premise of the practice of shooting longer shells in shorter chambers to begin with, that being that the longer shell must produce a pressure in its designed chamber length that would be appropriate for the shorter-chambered gun. Bell's test showed that even the 3" hull, if loaded to appropriate pressure, didn't cause drastic pressure increases in the short chamber, but generally speaking, 3" hulls are never loaded to appropriate pressure by any manufacturer.

(JDW:)Also you stated that older guns were never in proof even when they left the manufacturer. Wrong, they tested their guns before leaving the factory with loads that were twice the powder and shot of the loads available at the time. (Hunter Arms Co.) They just never put any proof mark on the barrels until the 1920's on some.

I'm quite aware of that, and later on they even marked them as such. But try and sell one of these guns to the gentleman in England who brought the subject up. You won't be able to because they won't accept it (i.e.illegal). They are most assuredly NOT in-proof as to their definition, and that is what I was addressing. In-Proof means a Proof House has certified it and it has not been altered or damaged since, not just the manufacturer's assurance that it is OK (which I am personally fine with, by the way).

"The reason we don't do this is the inherent PRESSURE of the shell, even when fired in a 3" chamber, not the length"

(JDW:)Actually the pressures in a 20 ga. 2 3/4" Heavy Field Load 1 1/8oz shot is equal to the pressures in a 3" of 1 1/8 oz of shot.(Lyman's 5th Edition) 2 3/4" shells also had Magnum written on them.

Again, the premise REQUIRES that the longer hull must generate a low enough pressure in its proper chamber to be appropriate for the shorter chamber (I don't have Lyman, but I'm willing to bet lunch that neither of the two loads listed are low pressure). If you skip this requirement, then the whole thing is null and void, and the discussion meaningless, and yes, all your comments on the danger could be realized.

I certainly didn't mean to offend, but I guess what I was trying to do is explain that the example you gave violated the premise the whole practice is based on. If you HAD stated 3" LOW PRESSURE, I would have said that the only data available says "no big increase in pressure". In the end, all we have to go on is data, and gut feelings. Your gut feelings obviously tell you not to do it, and that is great. I would never encourage you to. But there is NO data that I've seen that supports it. Those in the "don't do it" camp seem to imply that it is common knowledge and only a fool would try it. My question, then, is if it is common knowledge, where did we get it from? Someone had to have proved it once, right? I would just like to see those results so I can make better decisions in the future for my own practices.

I would not stick a factory 2-3/4" shell in a 2-1/2" gun because we don't know the pressure, but we do know that it could be (and likely is due to the popularity of autoloaders) near or at SAAMI max. But careful reloading practices ensure that we CAN know the pressures of our handloads (and control them) and it is ONLY then that the option becomes available. (Plus the exception of the few boutique factory loads that have published low pressures).