NP - hull length is not definitive of the shell. The pressure of the loaded hull and the match of that pressure to the design working pressure of the gun is much, much more important. Unless you are satisfied that you have identified the intended working pressure of the gun and the pressure of the load, simply put, don't use it, no matter the hull length. For example, I use my own low pressure reloads in 70 mm hulls with 7/8 oz shot charges in 65 mm chambered guns on a regular basis. The guns all have current Brit 1 1/8 oz proof, so I know the working pressure. I do all my own reloads, so I can keep pressures well below the proof pressure. I will shoot correct length CIP factory loads in these guns, but not longer. I will NOT shoot any SAAMI loads unless the factory is willing to tell me the pressure - some factories' pressures are known, most are not.
A longer hull is likely to raise the chamber pressure somewhat. The higher the pressure of the load, the more you are likely to see a bigger change. Note that shot charge weight and dram equivalent/muzzle velocity do not tell you anything about the chamber pressure. Pressure can be known only from a formulation that specifys hull, primer, powder type, powder charge, wad, and shot charge and lists a measured pressure. If you are not reloading, then you must rely on the factory for pressure information.
Further note that high pressure can be detrimental to hinge pin and hook, locking mechanism, and action. High recoil can be very damaging to wood.
Last edited by Rocketman; 10/30/07 12:57 PM.
