Special thanks to J.K. for funding this test in full. Cartridge : Federal 300 grain SP (Speer Hot-Cor SP) Firearm : American Derringer Model 4 (.45-70GOV) with 1.5" effective barrel length Block calibration : All depths corrected (From 11.2cm @ 586 ft/sec (Block 1) and 8.6cm @ 588 ft/sec (Stopper block)) Single shot fired from 6" distance. Bullet impacted at unknown velocity, penetrated to 26.3" and expanded to 0.614" average diameter. Bullet recovered at 287.0gr weight. If you look close at the picture below, you can see the grains of unburnt propellant in the wound track and on the front face of the block.