Before you crank out elephant loads, remember the old style rifles were killing bison (they are quite big if you have not seen one) and that load is frankly a cupcake. I have fired it both in the Marlin Guide Gun and Ruger #1. Subjectively, it felt like a 20 gauge to me. You can still buy the 45-70-405 off the shelf today, in smokeless powder. Or at least they have Remington ammo in stock at the Scheels in the capitol city in my state.