I'll buy that for a dollar. The expansion is what makes this very difficult to figure. What if we use solids? A flatnose solid will definitely damage a lot more medium than a bore rider needle point per about every ballistic guru of the last 120 yrs. How does that figure? Elmer Keith and Taylor all figured nose shape into knockdown values. Their research is a few years back but is still well regarded. The only way to test shape in a medium is with a solid. Otherwise we are testing EXPANSION not SHAPE. Whats our take on that?
A solid of the same diameter as an already expanding bullet striking the target at the same velocity with the same energy will have essentially the same effect.
If anything the rounded shape gives you a more even distribution and directionality of the shockwaves.
The same is true with respect to direct tissue damage at subsonic speeds, a .45 caliber hole is a .45 caliber hole whether it's round, square pear shaped oblong yada, yada, yada.
You can make an argument that jagged edges of separated petals or torn jackets do more cutting but they don't cut beyond the total circumference of the projectile.
Now when bullets fragment you get multiple smaller individual wound channels in the path of each individual fragment but those are much smaller wound channels and due to the rapid loss of velocity of the smaller fragments it's more limited.
There's certainly an argument to be made that with highly frangible bullets you can directly lacerate more tissue than with non frangibles but that's a completely different discussion altogether. Those bullets tend to perform very well as long as they aren't having to penetrate deeply or pass through heavy bone before getting to the vitals.
On deer for example the Nosler BT's work great for heart lung shots but can also result in horrible shallow wounds if you try to punch them through the shoulders of an elk sized animal or when trying to shoot them through the shield of a big boar.
Solids and controlled expansion bullets on the other hand punching through a deer's ribs and chest cavity without striking the spine or heavy bones can result in a deer running a quarter mile or more before expiring.
Two years ago we tracked a deer shot with if I remember right a partition that had punched the ribs missing everything else for over a half mile before finally losing the trail completely and we were using six experienced hunters and two very good blood tracking dogs. He may have only gone another hundred yards or so but he had left the property. He was shot on the neighboring property to the west, made it a half mile all the way across my property, and we lost the trail right where he crossed the country road on the east side of our property.
Bullet selection and placement are both key to quick, humane kills.
If you punch the same exact non expanding or limited/controlled expansion bullet through the shoulders and spine instead of the ribs that buck wouldn't have taken a single step and would have been dead within a couple of minutes at most, and more likely a few seconds of hitting the ground.
A ballistic tip in the same situation punched through the ribs and heart without hitting big bones and he doesn't run more than a few yards.
Match the bullet to the game, and your intended shot placement and about the only way you fail is if for some reason the bullet fails to open or you fail to put it in the right spot.
Unfortunately for most of us we are ingrained from an early age by whomever introduces us to hunting to shoot for the same spot every time without consideration to the species or the bullet we're using which results in a lot of "bullet failures" which are nothing more in reality than us failing the bullet.