Correct me if I’m wrong Ed but the original post states each pill is 200gr and the impact velocity is the same.
KE=0.5×m×v2
Plug the same mass and same velocity for the three different calibers into the KE equation and the energy is the same for the three pills.
I’m an energy guy to a point but not the traditional more energy equals more killing power. I believe it’s how the energy is transferred. So where the original question gets really grey is the form factor of three different pills (different calibers) can not be the same.
Example to the extreme
View attachment 6102
View attachment 6103
Two hammers of the same weight in different calibers. The form factor is completely different. The energy that’s transferred will be completely different in my opinion.
I also think the mass (animal size and resistance) that these pills impact will affect the outcome. As well as the impact velocity to a degree. Shoot a rabbit with these two pills and the 375 will likely cause more tissue damage. Shoot a moose with these two pills and I believe 264 could cause more tissue damage. At some point the 375 “pancakes” on impact with too much resistance, the energy transferred is wide and short. The added resistance of the moose contains this wide short energy whereas the more concentrated, longer narrower energy transfer of the 264 could cause more tissue damage with the added penetration. That doesn’t mean it’s a good moose pill but hopefully explains my thoughts on energy transfer.
Edit to add: the above is the reason we move to heavier weight pills for larger, heavier weight animals.
To add, who’s going to be able to accurately measure tissue damage? I believe it would have to be enough of a difference to visually see the difference. So “no replacement for displacement” to a point in my opinion.
I’m not even going to get into cup and core pills in this discussion as I believe there are many more grey areas concerning makeup and energy transferred.
Just how I see it
Kneedeep
. They don't make Absolutes in big calibers. They lose their efficiency above a certain point. Was hoping for a lighter HHT, but Fordy says the first cut was a failure
.
) & I need to get rid of the 124hh pills( 6.5&30 cal ) that are gathering dust lol 
