Originally Posted by Ruzai
Like you stated energy will tell you what type of wound the bullet will make
Sorry for the confusion, but I actually said the opposite. Energy itself tells absolutely nothing about the type of wound channel a projectile will make. Literally, nothing heh.
A 55gr bullet at 3000fps from an AR15 is about the same energy as a 300gr bullet at 1300fps from a .44 magnum.
The .223 bullet could be solidly-constructed hunting bullet that holds together, expands to maybe .4", and penetrates to about 15" in gel. It could also be a varminting round that fragments significantly and penetrates to maybe 8". In either case its velocity will cause permanent damage well beyond the actual projectile path.
The 300gr .44mag bullet could be a hard-cast that will literally penetrate about 6 feet of flesh. Or, it could be one of the well-expanding rounds that will expand nicely and penetrate about 3' of flesh. In either case, its low velocity means the only permanent damage will be what the bullet itself physically touched along its path.
So again, the only way to formulate an accurate estimation of wound potential is to know velocity, mass, and bullet construction (which is related to caliber). With those, energy can be calculated, but the energy itself doesn't tell you anything.
Think of it like walking into a Dodge dealership and choosing which vehicle will be fastest around a racetrack based ONLY on horsepower. You might end up leaving with a 500hp Diesel-power Ram that weighs 9000lbs, when the 2500lb Neon SRT-4 with 240hp would run circles around it. Just the same, if you are looking for the vehicle to tow a boat, you might leave with a trade-on C6 Corvette with 600hp, when in this case a big truck would have been way better. Horsepower itself, just like bullet energy, doesn't tell you anything about how a specific car (or cartridge load) will perform a specific task.
And it doesn't take specifically-frangible bullets to fragment or expand significantly. There are lots of light-for-caliber (90-110gr) .308 varmint bullets that will do this when pushed to proprtional velocities (say, 3200-3300fps).