Gibbs and Mashburn cartridges.
I wondered if anyone on this forum is using the Gibbs cartridges. I'm interested in both cases and reloading data for an article I am writing.
I'm also interested in the Mashburn cartridges and info on them.
I've never owned them, but many years ago I reloaded for a friend's 6.5 and 30 Gibbs. I'm kind of surprised they haven't experienced some kind of rebound in recent years. I never felt the powders available in those days did justice to the extra case capacity. It was the old surplus 4831 all the way, with 4350 a distant second. The wide variety of slower powders available today would be nothing but good news, I think. I think that in particular would be fruitful ground for your research, but I'm not curious enough to have rifles made for them now. I checked, and I don't have the loading data any more. It went with the friend when he moved over 30 years ago.
We have a Gibbs Mauser rifle here marked .256 Gibbs Magnum. Bore IIRC is .266 and it may have been rechambered for .264 Win Mag
The .256 Gibbs Magnum is an English designed case. Here are the specs:
Bullet dia; .266"
Case dia. -neck; .300"
Case dia - head; .472"
Case dia-rim; .475"
Case length; 2.154"
Bullet weight; 145 grains
Muzzle velocity; 2600 fps
Introduced by George Gibbs in 1913 and based on the 6.5mm x 55mm Swedish round.
These days it is a very rare chambering.
Still looking for cases, especially these: .240, .25, .270 Gibbs and 7mm and .350 Mashburn. Other wildcat cases are of interest too.