doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com DGJ Article on Chamber Length/Pressure

I have been trying to find the article by S. Bell on his research on shooting regular length shells in shorter chambers. I believe his research indicated that, as long as the shooter was mindful of the pressure generated, there was little or no increase in pressure from the longer shell in the short chamber. I don't have a good index on the DGJ and am missing some issues. Any help would be appreciated. Thank you.

The articles in SUmmer and Winter 1999 are probably it, but I have see other articles that have comparative PSI's that I can not find at this time.

I did an article for Shooting Sportsman on that subject, Jan/Feb 02. Pretty sure I cited some of Sherman's experiments.

You've got the general thrust of the issue, Gil. Sherman's articles include specific examples of pressure increases as a result of a longer hull in a short chamber. He even shot some 3" shells in 2 1/2" chambers! The resulting increase in pressure was usually a few hundred psi, and Bell also found that lengthening the forcing cone often negated some of that extra pressure.

Winter 2001 Double Gun Journal has the article by Sherman Bell called "Finding Out for Myself" Part V "Long Shells in Short Chambers".

Thank you for your input. With your help, I was able to go right to that issue. gil

Mr. Russell, there is another mention of a similar test in Garwood's Gough Thomas's Gun Book starting on p.260. It might be worth looking at if you want another reference.

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G.T.Garwood's article arose from a controversy in the 1960 when Eley-Kynoch started loading their Grand Prix game cartridge, intended for 2 1/2" chambered guns, in a 2 3/4" case with a crimp closure. There was a lot of correspondence generated in the sporting press at the time as to the possible risks of such a practice. Tests showed that there was no real discernable difference provided that the loads were kept to the same overall pressure. Lagopus.....

This work was actually started just prior to WWII in England with the introduction of the fold crimp clousure. It was completely finished just after the war & fully reported on by Burrard at the time. Both Thomas & Bell could have saved a lot of time & trouble by simply reading "& Understanding" his work. Both took statements of his concerning "True 2 3/4" shells loaded to a higher pressure level than the standard 2½" shell out of context & attempted to make him appear wrong. Even today shells should not be fired in a gun, regardless of chamber length, loaded to a higher pressure than the gun was intended for.

There is more variation in forcing cone shape and diameter in various guns than the thickness of a modern plastic shell. And that thin plasic shell intrudes only 1/4" into the 2 1/2" chamber's forcing cone at the largest part of that cone. Is it hard to imagine that there is no appreciable difference in pressure when shot in either a 2 1/2" or 2 3/4" chamber?

The problem with Burrard and Thomas--both of whom had it right on the issue of long shells in short chambers--is that they can both be quoted out of context to make it seem as if they were wrong. One has to read all of Burrard's "Length of Cartridge" section, and all of Thomas' "Danger in Case-Length" chapter, to understand fully what they're saying.

It's also useful to remember that it was less common to find loads that met CIP pressure standards in 2 3/4" cases back when Burrard and Thomas were writing than it is now. There are all kinds of 67/67.5 MM cases out there now--some of which measure the same length as American 2 3/4" cases--loaded to standard CIP pressure. And it's even stated, right on the cartridge box, that such shells are appropriate in guns with 2 1/2" chambers.