The 30-40 Krag was the 1st US Military round designed for smokeless powder. It will develop 39,000 CUP. The 45-70 loaded for the trap door rifle will develop 28,000 CUP. Loaded for a Ruger single shot and the pressures quickly jump into the 30-06 range. IMR lists a 1 1/8 12ga load at 1250 fps at 11,000 PSI. The same load can be loaded down to 8,000 PSI.

As for the firing pin. It should be bushed during the conversion. This is just common sense to prevent the primer from flowing back.

Some years ago, I purchased a set of 45-70 inserts from MCA Sports . At the time I spoke to him about loadings. He stated flat out, "Keep the handloads in the trap door range."

Pete