doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Safe to use 2 3/4" lite loads in 2 1/2" chambers ?

Several issues at work here:

1. What's the definition of "lite loads"? Most would characterize a 7/8 oz load, regardless of hull length, as "light" in a 12ga gun--but it might not be light in terms of pressure. Or it might be.

2. What's the definition of "the ammunition the gun was designed for"? I have several boxes of British shotshells, some of them 2 1/2", some 2 3/4". The information on the shell boxes tells me that the 2 1/2" shells are appropriate for guns with 65mm/2 1/2" chambers or longer and marked 3 tons. However, the Brits didn't start marking their guns with the "tons" marks until 1954, which leaves it open to question whether guns manufactured prior to 1954 were designed to handle those shells.

3. What we do know, from Sherman Bell's tests as published in Double Gun Journal, is that using hulls slightly longer than the chamber in question does raise peak pressure somewhat. Usually only a few hundred psi, although in some cases a bit more than 1,000 psi.

4. What we also know is that the Brits themselves, for quite some time, have used factory ammunition loaded in hulls that are slightly longer than the chambers in question--without raising pressures to dangerous levels.

My own conclusion from all of the above: IF you know what you're doing and IF your gun is in sound condition, there will probably be no problems using standard 2 3/4" hulls reloaded to the pressures for which the gun was designed--and building in a "safety cushion" to compensate, just in case the longer hull does increase pressure somewhat--in guns with 2 1/2" chambers. The most common exception is in older (pre-1900) guns with very short and sharply-tapered forcing cones. With those guns, there have been reports of even factory British ammo in slightly longer hulls causing problems, such as blown ends on the shells. In those guns, you do need to stick with true 2 1/2" hulls, whether factory or reloaded. But in all the short-chambered guns I've owned, I've yet to encounter that problem. And like Chuck, I reload 2 3/4" hulls to appropriately low pressures and shoot them in my 2 1/2" guns.

What L. Brown said.
One other personal observation; it does feel to me that 2 3/4" shells in a 2 1/2" chamber raise recoil levels a little. Even with identical payloads and velocity. Maybe its just me, but I do notice it.

The data from many tests indicates that there is only a slight increase in pressure(100-500psi) from using the 2 3/4 " loads. I have never noticed any increase in my 2 1/2 guns.

Teeny, what shotgun do you have?

Quite aside from safety concerns, I found that a 2 1/2" chambered gun patterned poorly with 2 3/4" shells. Whether this was the result of shell length may be impossible to know, but it nudged me to use ammo of appropriate length.

Patterning the difference between the two is an interesting question. I will try that and check the difference. FYI,I always shoot ammo with less that 7000psi in my older doubles.

Stan, I missed the wall in his description of his measurement. I still think teeny needs to delve deeper into the best methods for appraising barrel integrity. Even a wall thickness measurement 9" from the muzzle isn't that relevant.

Stallones, you state "the results of many tests" show there is only a slight increase. What tests, where can we see the results?

Also you said you never noticed any increase in your 2 1/2" guns. Were these guns equipped with pressure sensors or how would you notice any increase in your guns?

Stephen Grant side lever & Charles Boswell 2 1/2 " both proofed for nitro

Steel barrels

Nice guns,teeny.