In looking for some guidance on pressure for DR's, I looked in "Shooting the British Double Rifle". I think on about page 115, he discusses guidelines but they are in tons per square inch. First question is whether he was using the 2000 pound ton or the metric ton (2200#). I am trying to convert it into PSI.

Looks to me like the standards Graehme is using would fall under 30,000 PSI. Is this realistic or too low for modern doubles?

I was corresponding with Norma powders a while back on their published MRP-2 loads for the 470 NE. The max load of 128 grains (15% compression) was off the chart on my ballistics program. Norma measures their pressure in mega paxels, but after a kind soul converted their readings it was over 36,000 PSI. Even their reduced recommendation of 113 grains (2150 fps) ran at between 32-34,000 PSI.

Now I would love to find a powder that fills the case and gets the right velocity. But I can find little, outside of the British Double book, to provide any guidance on pressure.

Thanks