Owner of Buffalo Bore Tim Sundles on Heavy 44 Magnum Ammunition:
Item 4B (300gr. JFN) is designed for super deep penetration at revolver speeds, but will mushroom and penetrate less deeply at rifle speeds. At handgun speeds you can expect a solid 3 feet of penetration in muscle and bone and at rifle speeds expect roughly 2 feet of penetration in muscle and bone. At handgun velocities, this bullet will act just like item 4A in living tissue. The greater velocities generated by the longer barrel of the rifle will cause the bullet to mushroom and that large mushroom will make a much bigger diameter hole in tissue, but that frontal area on the mushroomed bullet will cut down the depth of penetration.
You’ll note my below velocities form over-the-counter revolvers and rifles.
Item 4B is recommended for all STEEL revolvers and rifles on today’s market. It is NOT suitable for scandium or aluminum alloy revolvers.