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

Maybe Chuck, but I always thought English folks were capabile of such all by themselves. When folks are calling 2 9/16 and 2 5/8 inch chambers "2 1/2", I would think they are already safe from rational advantages of metric system. Is excentric a good word here? One that Brits are proud to wear?

Don't forget that even USA's NASA has been reported to have sometimes been unable to square the metric units with English ones, with notable failures resulting.

Niklas

Dave, thank you! I am very happy to be in this company, :-)

Best to you too.

JC(AL)

There seems to be an understandable confusion among many posters as to the use of proof terms as a historical point of reference and the way that modern ammunition manufacturers cater for these.

A British gun stamped 2 1/2" or 65mm or with a diamond with a 'C' inside it (which mark you get depends on the age of the gun and when it was proofed)is designed for a 'normal' game load.

It is proofed (and in some years also stamped) with a service pressure of 3 tons per square inch. You need to consider the 2 1/2" chamber length, because you do not want the end of the crimp entering the forcing cone, failing to open fully and therefore increasing pressure. Ammunition in cases of 65mm, 67mm and 67.5mm is olny allowed to develop pressures in keeping with guns proofed at this (lowest) proof test.

BUT

You also need to be aware that modern 70mm cased shells are allowed to develop higher pressures because a gun stamped as proofed for 2 3/4" shells will have longer chamber, thereby acccommodating the crimp and allowing it to open fully but also because the proof pressure for these guns is done to 3 1/4 tons per square inch.

Therefore, a 24g 70mm shell may have a lower pellet payload than a 30g 65mm shell but it may well produce higher pressures.

In the UK, this is common knowledge and no shooter would put 70mm cased shells in his 2 1/2" game gun any more than he would put diesel in his motorcycle.

A few cases in poit:
My 1889 Purdey - has 2 1/2" chambers and is proof tested to 3 tons per square inch. In it I regularly and safely use the following:

34g bismuth shot loads 'Eley Maximum' brand in 67mm cases in boxes marked 'Suitable for guns proofed for 2 1/2" shells'.

30g Game Bore Pure Gold lead loads in 65mm cases marked as above.

24g Express HV lead loads in 65mm cases,marked as above.

I do not use:

White Gold 28g lead in 70mm cases marked 'suitable for use in guns proved for 2 3/4 inch shells' because although they are lower in pellet weight, they are more powerfully charged and the cases will not open fully in the chambers of my gun.

That same goes for any case marked 70mm or 2 3/4".

I hope that helps a bit - and I apologise for the grumpy tone of my earlier (early morning pre-coffee) message - I stand by what I said but I should have worded it more respectfully.

Smallbore
After reading your post above, I can see your perspective and why you posted your thoughts in the earlier post. UK logically limits pressure standards to progressively higher pressures for progressively longer shells. Simple, logical, and fits with the progression of both shell length and gun strength. From what I've learned here from our more historically aware members, American shell length progression and pressure progession follow a similar path.

However, in my earlier post, I was referring to reloading. As such, pressure can be controlled regardless of shell length. Since I have an instrumented test gun with a chamber that matches my field guns intended to use the reloads, I have relavent data regarding any restriction that may increase pressure due to any constriction caused by a long shell/short chamber.

From your perspective, I'm sure you are still wondering WHY? Why would I want to do this even if it's possible to do safely in this manner? Well, it's probably been a long, long time since I saw a shell less than 2 3/4" in my part of the country. I could order them for something like $8-10 a box and get whatever load the mfrs chose to offer. But, being of the type that likes to go my own way often, I chose to work up my own low pressure loads, the long shell, short chamber was simply a matter of bypassing a step (cutting long shells down) if I can get the same performance.

With my limited testing, I've convinced myself that it's a practical and safe approach and eliminates a trimming step in the reloading of the only commonly available length of shells here. I've also done enough pattern tests to believe the pattern is good out of my guns with these loads.

Smallbore

You need to chill out bud. Nobody on this board is advising anyone to shoot anything. They are simply stating what they practice or have read.

Maybe you should try preaching to those who participate in some seriously dangerous sports such as mountain climbing or auto racing. Plenty of people actually die every year in those sports.

The folks shooting 70mm shells in 65mm guns have no desire to make excuses for what they do so you don't need to excuse them.

Can we all be dismissed now kind sir?

Jim

A couple of points:

First, everyone seems to assume that Mr. Bell has no "degree" in engineering, therefore his research is invalid. I have corresponded with him on numerous occasions, and can confirm that he is, in fact, a degreed engineer. Even if he weren't, I've seen recent research (in other fields) from degreed scientists that was pure junk, and I've seen other research done by laymen that was flawless. A degree doesn't equal competence, it's just a starting point. I immediately see red flags when someone tells me to "believe what I say because I have a degree". I have those degrees, too, and I know colleagues with the same degrees that I wouldn't trust to have sense enough to come in out of the rain. They are the ones who seem to crow the loudest about their degrees (insecurity, perhaps?).

I have seen the term "fools" and similar used in this thread describing the practice of using longer shells in shorter chambers, even though they are low pressure. I have seen real data produced to support the practice from several sources done by different organizations at different times (eras, even), but oddly, NO data of any kind that shows it to be unsafe. If it is such an obvious danger, where is the data that shows it? Surely if it is such common knowledge, someone had to have proved it somewhere. In the case of Bell's research, they used an industry-standard test barrel (Mr. Armburst's), not some home-made device. If that data can't be trusted, then how could we trust any data from the industry?

Someone already pointed this out, but the analogy of 2-3/4" shells in 2-1/2" chambers is the same as 3" shells in 2-3/4" chambers is completely ignorant of the situation as it exists. There simply are no low-pressure 3" shells produced anymore (they all say "magnum" on them). The reason we don't do this is the inherent PRESSURE of the shell, even when fired in a 3" chamber, not the length.

Someone mentioned that it was equally stupid to shoot a gun that is out-of-proof. OK, then most of the early American guns are out of the question, because they were never in-proof, even when they left the manufacturer. But do we really believe that these stout-barreled, heavy guns can't handle the pressures of the little lightweight British and European game guns of the same era with proof marks on them?

If you feel, or "know" that the practice of 2-3/4" shells in 2-1/2" chambers is unsafe, or you just aren't comfortable with it, then fine. I support your decision to avoid the practice. But unless you can provide data to prove the results, please refrain from the smugness and name-calling. As the saying goes, money (or data) talks, and the other stuff...walks.

I just re-read what I wrote. JEEZ I've gotten crotchety. It's gotten way too late and I've got a gobbler to chase at dawn tomorrow. I'm off to bed, so no more tirades from me to suffer through. I'm sorry, fellas, I'm really not that grumpy!

Ever messured shells after firing?
67,5 mm shell becomes 70 mm shell after firing.
An if you reload it again, you will reload 70 mm shell allready.

Well before Bell ever ran his "Finding Out for Myself" tests--which provide still more confirmation of the practice--the late British gun gurus Maj Burrard and Gough Thomas both reported on the practice of shooting 2 3/4" shells in 2 1/2" chambers, which has been common in Great Britain for some time (provided that the shells in question were made within the pressure parameters appropriate for 2 1/2" guns). And both Burrard and Thomas concluded that the practice was perfectly safe--although in Burrard's case in particular, he can be misquoted on the subject if you do not read ALL of what he said. Thomas gives the actual pressure figures for a 10-shot string, 2 3/4" Eley Grand Prix shells fired in a 2 1/2" chamber; same in a 2 3/4" chamber. There is no difference in pressure and velocity from one to the other.

It is very easy to reload 2 3/4" 12ga hulls, especially 7/8 oz target loads, to pressures of under 6,000 psi. At least here in the States, most of the 2 1/2" shells we can find are field loads vs target--heavier shot charge, greater velocity, greater pressure. So chances are you're actually doing your old gun a favor by shooting low-pressure 2 3/4" reloads in it, unless you can find a good source of low-pressure factory 2 1/2" shells.

Well said, Larry!

Well it seems that some people are going to shoot the longer shells in shorter chambers anyway.
On some of the drawings of the forcing cones, and the length given of the chambers by various manufacturers, I'm still going to abide by using 2 1/2" low pressure shells in 2 1/2" chambered guns because I still don't believe that the longer shell opens fully creating more pressure.

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.
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.

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

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.
Yes the loaded shells do cost more to buy, but there are companies out there that sell componants including 2 1/2" shells for reloading.

It's like one previous poster said, why encourage someone that is new and has a 2 1/2" chambered gun to shoot longer shells in a shorter chamber, it must be ok becasue he read it here.