None of this says hammers are good bullets, I have not used them.Not sure why anybody would shoot a hammer…unless you’re required by law. The design calls for a caliber size entrance and a caliber size exit and significant shedding of weight. If I could describe my least desirable performance in a bullet, this would be it. 2 caliber sized holes with significant loss of weight.
Velocity (roughly above 2000 fps) results in a temporary wound cavity large enough to damage elastic tissue. Most rifles, regardless of bullet, cause more damage that a caliber sized hole.
In low velocity rounds (most handguns), the only damage is in the permanent wound channel, and this is always smaller than final bullet diameter because tissue stretches. The more pointed a low velocity projectile, the smaller the permanent wound channel.
Hard cast handgun bullets have a flat meplat to get better penetration while having larger permanent wound channels. The fat meplat also improves stability in tissue, which increases penetration.
So, from a low velocity perspective, the hammer design should maximize permanent wound channel size will providing good stability for maximum penetration. From a wounding perspective, this can be good or bad, a bullet that goes through lung tissue sideways will do more damage, but if it turns sideways too soon it might not make it to the vitals.
In short, theory must be verified with results to be substantiated. That, said, life is too short to test everything, so theory is certainly a valid place to start.
An interesting aside were theory failed me. I butchered a pig recently. Figured a 230 gr gold dot from 4 inch barreled 45 at 6 inches would get to the brain. Three shots behind the ear going for the opposite eye latter and the pig is still standing. 4th shot was to the top of the head and dropped it. I figured I was an idiot and had my shot angles wrong. However, I found my bullets up against the back of the skull, they simply cound not go through the inch of bone.
The one in the top of the head had thinner bones to go through, it still did not travel more than 6 or 7 inches.