doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shell Length Confusion

The treatise here says the difference between a 2.5 inch shell and a 2.75 shell from a 2.5 chambered gun amounts to an increase of 300 -400 (on average) increase in psi, insignificant.

Does that translate at all to 2.75 and 3" shells?

The variables in the equation are a given. Each length shell is loaded to the same configuration.

Take a 2.75 magnum shell at 1500psi with 1 1/8 shot from a 2.75 chamber. That is a standard 3" shell. Is there an increase of pressure if you were to shoot the 3' from the 2.75 chamber?

1500 psi???

I wondered about that one too Larry.

Two things to keep in mind any time you shoot a shell longer than the chamber is;
1st, that the load is appropriate for the gun with the shorter chamber.
2nd, is that the loaded shell does not enter the forcing cone restricting opening of the crimp, there must be clearance between the end of the loaded shell & the cone allowing free opening of the crimp.

One can find modern 2&3/4" shells (Winchester Featherlights, Fiocchi extra low recoil come to mind) that will have lower avg. gas pressure than some 2&1/2" game shells. The same does not hold when selecting modern 3" shells vs. 2&3/4" ones therefore using modern 3" shells in gun with 2&3/4 chambers would be stupid.

2 1/2" chambers are frequently English guns. It was the standard size, and 2 1/2" cartridges are widely available here. What you should be aware of is that 2 1/2" is a 'nominal' figure.

There are several factors as the different gunmakers used different actual chamber lengths and different forcing cone profiles. Also the older guns were designed with roll closure cartridges being the norm. These are shorter than crimp when opened.
Many nominal 2 1/2" chambers are actually more like 2 5/8" and have gentle cones, so are quite tolerant of a cartridge greater than 2 1/2" when opened out.

However some have short sharp forcing cones, starting quite near 2 1/2".

Therefore it is not safe to generalise and say only a small pressure rise will occur using the longer cartridge. That may NOT be true in all guns. Each gun needs to be considered separately.

I know of a case where a nice Boss gun was put off the face by a day shooting 2 3/4" cartridges that were within the load limits of the gun proof (1 1/8 oz) but just too long a case - and the high pressures caused damage.

Fascinating! I wonder what the factories are thinking when they stamp a chamber length on a barrel and then make a cartridge specifically tailored to that chamber dimension? Much like those ridiculous markings on factory choke tubes that state "not for steel". When will those fools finally admit that shooters are far more qualified to assess what is proper or not than the makers ever will be.

Wonko, would that be like the guidance that one should never use smokeless powder loads in guns with Damascus barrels? Funny that said warning doesn't say anything about Damascus barrels that have passed nitro proof.

As said previously - I'm certain that the shooter is far more qualified to make those assessments than any self-appointed authority. Your gun, your face, your hands - - who could know better?

DEFY AUTHORITY !!! WTF do they know, anyway?

Note that since about the time WWII ended shells have been purposely & intentionally loaded in England into hulls longer than the 2 1/2" chambers they were intended, & so marked, to be used in. But what do they know, they're such dumb Brits who "Never" ceased proof marking Damascus barrels for use with smokeless powder.

Note these longer shells were all closed with a "Fold" crimp, thus there was clearance between the end of the loaded hull & the cone, the big secret to using a longer hull than the chamber. The loaded shell should "Never Ever" actually enter the cone restricting crimp opening. This was all settled some 70+ years ago, why dispute it now.

Accounts of all the work done at that time can be read in "The Modern Shotgun". Note that Burrard neither developed the principal, nor did the testing, he simply reported on the vast amount of testing done by the major shell makers of England such as Eley etc.

It is too bad a few people were simply Too Ignorant to understand what he wrote, would have saved them a heap of trouble. Or perhaps they did understand but just wanted to act like they discovered it to try & make a Big Name for themselves.