Brass, Bismuth, and nitro powder

[Laurence Frank]

New guy here.

I am curious about using RMC brass shells with nitro powders for modest pressure 12 bore bismuth waterfowl loads and have had little luck finding information. RMC tells me that any recipe for plastic shells and wads is ‘safe’ with brass, but how are pressures affected by fiber wads and overpowder and overshot cards? These would be for nitro proofed Brit fowlers. I’d be grateful for any advice and recipes.

Many thanks.