doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2 1/2" chambers and 1" cones

Wow! This subject has been beat around so much it's beginning to look like four day old roadkill on I-40....not much left to look at. Been fun though.....we need more "knock down and drag out" topics like this to take the boredom out of the summer doldrums.

What's next? small bores vs. real guns? Sounds like a vinner to me. I'll start it: been my experience that all 20 gauge guns spend the rest of their life wishing they were a grown up 12.

There's really no comparison...small bores are for women and children

Hi Larry:

17 going on 18, starting to slightly crack.......20 ga. 2.5"......... try to think outside the box if you know how..............

Sure is contradictive that you state these facts are never reported on this BBS, when on 9-13-08 @ 5:29 PM --L. Brown, you, wrote the following:

"I think a reasonable conclusion is this: mouth of the unfired hull extending into the bore itself, or into a very short and sharp forcing cone, may very well produce dangerous results in terms of pressure spike, visual damage to the hull, and perhaps increased recoil" .........WORDS OF L. BROWN.....

So, I guess you have known about problems all along and have read the reports over the years, but choose selective memory regarding these facts......?........







One of 'several' special steps..........

Doug, if the mouth of the shell extends into the BORE--that is, PAST the forcing cone (note that when you measure BORE diameter, you do NOT do it in the cone!)-- that would indeed be a potential problem. But we all know equally well, don't we, that it is highly unlikely for that to happen. Unless, of course, you do something like maybe shoot a 3 1/2" shell in a gun with 2 1/2" chambers. (If you could close it on one of those.) Or run across a gun with extremely short forcing cones.

As for the part about the short and sharply angled forcing cone . . . darn Doug, you must have a lot of time on your hands. If you'd simply read this thread, you would note that I pointed out that SOME guns--likely very old ones (pre-1900)--shouldn't even be fired with the 67MM/67.5MM shells, which the Brits and other CIP nations sell for use in 2 1/2" guns all the time. With the blessing of their proofhouses, I might add. Charles Fergus, in a long ago issue of Shooting Sportsman, reported that problem with 67MM shells in an 1880's or 1890's Brit gun he had, while the same shells functioned just fine in a 2 1/2" Brit gun from the 30's. And true factory 2 1/2" shells functioned just fine in his older gun. I'm not going to bother chasing down my ancient post, but I expect I might even have made reference to Fergus' report, therein.

That being said, the fact remains that the vast majority of 2 1/2" guns will work just fine with 2 3/4" hulls (none of which actually measure 2 3/4" when fired, and at least some of which measure no more than 2 5/8") loaded to appropriate low pressures. Were that not the case, the dozens of us on this BB who have been following that practice for a very long time would have reported problems, which you would have seen discussed here in great detail. But the fact is, it's a pretty rare 2 1/2" gun in which a fired hull will extend PAST the forcing cone and into the bore. In most cases, they'll barely reach the cone. And per data provided by an American back in the 30's, and by Burrard and Thomas, and more recently by Bell in his "finding out for myself" series, we know that that practice results in, at most, only mild increases in pressure--if we're talking a shell no more than 1/4" longer than the chamber of the gun in question. Most guns having a forcing cone of at least 1/4".

My question is what suffers? When you interject something else into the equation, there has to be an action/response. I'd guess the pattern suffers, but how much? Has anyone tried to pattern U.S. of A. #2s or #4s with 70mm cartridges in a 65mm chamber?

Kind Regards,

Raimey
rse

What does the "soak" of the case mouth do, Doug, soften it? Can hull plastic be hydrated, or is that not water?

Stan

Guess its hot water. There is recomendation I saw many times for reloading plastic shells, to make plastic softer by heating before smoothing out creases of shell throat.

At least with paper shells, Raimey, the patterns actually improve. Back when the conversion was made from short to standard 2 3/4" chambers in this country, it was standard practice for some of the top trap shooters to shoot longer shells in shorter chambers. The case mouth, opening slightly into the forcing cone, cushioned the shot (not protected in a plastic shot cup back then) on its initial contact with the bore. Of course that's no longer a problem with plastic wads/cups, but I don't know why a plastic hull opening slightly into the cone would hurt the pattern. According to the author of the article that's the source of this information (American Rifleman from the 30's) who was a long-time employee in the American firearms industry, there were several gunmakers who were actually short-chambering their 2 3/4" shotguns in order to give improved patterns with the ammunition then available.

Here's one example I have, from some patterning I did. Shells were fired in an Army & Navy with 2 1/2" chambers and factory forcing cones, barrel choked .004 (skeet), at 25 yards. The first was a Westley Richards 2 1/2" shell with 1 1/16 oz nickel-plated British # 6 shot; the second, my own reload in a Federal Gold Medal 2 3/4" hull, 1 1/8 oz American # 6 shot, standard lead. The WR patterned 62%, the Federal reload 75%. In both case, I did pellet counts on the shells in question before patterning in order to get accurate percentages. (Just found a 3rd example, same gun, same distance: Eley Grand Prix 2 1/2", 1 1/16 oz Brit 6's: 66%. Interestingly, while the Grand Prix had a fiber wad, the WR had a plastic wad (as did, of course, the Federal reload.)

If it is such a sucess, why hasn't the idea been nutured? I'd like to see data on large shot. Also if the 70mm cartridges were star crimped and the 65mm were roll, then the pattern would become more dense. Were yours star, roll or both?

In autos with chambers over 75mm for some reason the Rios(steel) tear the end off about every time.

Kidn Regards,

Raimey
rse

It could be explain by more powder charge forcing in long shells and in short chambers. But I don't believe in pattern improving, its all about much more pellets penetrating and more pegions clean killing.
With modern powders there is no suchs problems anymore.