Just my recollection of Bell's article, but I thought he said he tested paper hulls as well and they didn't show an increased pressure outside of the average of the plastic hulls. Also, my memory says that he got between 0 and 15% increased pressure from 2 3/4" shells in a 2 1/2" very short (1/2"???) forcing cone chamber.

My personal experience with only one load in a couple damascus guns is that my 2 3/4" Federal paper hull loaded to what a manual says should be mid 7K psi is actually coming out to mid 6K psi measured in a short chamber. I feel no significant recoil and velocities are super consistant at 1150 fps.

So, from all the above I've formed the opinion that short chambers (mainly 2 9/16 to 2 5/8" in American guns as I understand it) is not a reason to change my reloader setup to load 2 1/2" shells. It's inconvenient to change to shorter shells and I see no benefit at this time. However, if someone has convincing evidence that my information is wrong, I'm always willing to change that opinion.

I do have to take exception to the statement that pressure has nothing to do with recoil. I believe it is one of several key components in acceleration of the payload in a gun, the others being time and weight of the payload, and surface area of the payload upon which the pressure and time work to accelerate the payload and conversely, the gun in the opposite direction. I'm no physicist or ballistician, but I think that covers the basic physics of a gun. Sorry Pete.