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

Thank you Mike. One mystery solved. I think I will stick with the thin flexible Gun club 2 3/4" hulls from now on. They seem to hold up pretty well.

One thing I would like to insert into this thread;
"Years" prior to Bell & also some time prior to Thomas as well, actually the late thirties, British ammo makers pretty well settled this matter. Upon introduction of the "Fold"/"Pie" crimp overall length of the "Loaded" cartridge became shorter. To accomadate the same load internal capacity had to be increased. Whether they acomplished this by reducing base wad height, wad thickness or wall thickness or a combination of these I have no idea. Anyway there was then a fear that these shorter shells (nominal 2½") would be mistaken for 2" shells due to their shorter length. Subsequently, experimentation was carried out with case length to give a similar "Loaded" length to the older roll crimp shell. Testing revealed that as long as the load was the same pressure & balistics remained virtually unchanged. "NO" drastic change was noted in pressure, velocity or recoil. All of this is reported on by Burrard. This work was not done by Burrard himself, but by the makers. Burrard was not so Egotistical as to think results could only be determined by "Himself", but relied heavily upon those in position to "Know". I do not have any old fired English cases to measure, but it is my understand that from approximately WWII time on all British "Cartridges" "Designed to be fired from a nominal 2½" chambered game-gun closed with a fold crimp have a "Fired Length" longer than the chamber they were "Designed" for. "IF" this can be proved not the case I will then stand corrected. As stated several times here the answer is "Designed Pressure", not case length up to a point. The British's conclusion was shells should "NOT" be used having a "Loaded" length long enough to enter the cone, as this could very well inhibit the opening of the crimp, leading to excessive pressure.

2-piper, I do know for a fact that an opened 12 gauge, old style AA case is the same length as a Gamebore "Super Game" hull which states on the box that it is 67.5 mm and safe for use in 2 1/2" chambered English guns.
As I recall, the Gamebore kicked quite a bit more.
This was my first hint that paying $10 a box for special ammo is not always all it is cracked up to be.

Steve, for the # of shells you plan to shoot, cutting 2 3/4 plastic shells down to 2 1/2" and loading on a MEC progressive is not bad. It does require the 16 ga overshot card, but no other modifications to your press. Light loads made this way have less percieved recoil than most factory 2 1/2 shells. Others may disagree, but I have found light 7/8 oz loads will break any clay that I have the ability to hit.

"My mind is made up, don't confuse me with the facts".
This seems to be the prevailing philosophy.
Hopefully someone will answer Chuck's request
(but I honestly doubt the facts will come from the "engineers" out there).

I had the audacity to cite Mr. Bell's article in the 16ga. forum, when asking about this
same issue concerning my Manufrance Ideal prooved for "PRESSION 1100 KILOS".
I mentioned I was using 67mm shells loaded to CIP standards and received a sanctimonious
bashing for it.
To make a long story short, I was ostracised and frankly felt relieved.

JC(AL)

My goodness JC-I'm sorry if that was your reception on 16ga.com
Do you recall when you posted so I can look up the thread? And who was the 'basher'?

I entered this thread quite late, so please forgive me. If I am not mistaken, even though Mr. Bell may not be a graduate engineer, his partner in the investigation was Tom Armbrust, who I believe IS an engineer (ballistic engineer?). As a graduate engineer myself, I find no problem following documented and properly done experiments by a field experienced non-engineer, especially when assisted by an expert in that field. Following Mr. Bell's admonition, using shells whose PRESSURE IS DESIGNED FOR THE GUN, I find no problem with my 2 3/4 reloads (Federal paper hulls) which I make having approximately 6,000 psi in my older guns with shorter chambers (2 1/2, 2 9/16, & 2 5/8").

If anyone wishes to have a spreadsheet of low pressure loads compiled from various powder manufacturers' reloading handbooks, please send me a PM with your email address. I will send the multipage spreadsheet as an attachment to the return email. Jim Haynes

Revdocdrew, sorry, I do not remember. And I also apologize for not mentioning that
there were exceptions like Utah and surely yourself there, but.....

JC(AL)

This Eley catalogue page explains itself as far as case lengths go:



67,5mm for 2,5" guns.

JC(AL)

Seems like an excellent time to point out that 2 1/2 inches is actually 63,5 mm. And that 65 mm is 2,559 inches, that 2 9/16 inches is 2,563 inches (who wants to quibble with 0,004 inches?), that 2 5/8 inches is 2,625 inches, which is 66,68 mm (can we approximate this to 67 mm?).

Also seems like a good time to ask ---"Are there really any 2 1/2 chambers on those old double so marked?"

But, what is 1/16 of inch among fellow posters, especially in the midst of a lively discussion? Even 1/8 inches?

Niklas