But what about ligaments, tendons, and bone? Those are not highly elastic. Doesnt damage done to those parts of the body also factor in when judging "effectiveness"?
But also even
less likely to be affected by 'temporary cavity'.
Also what about the 545x39? how does that compare with the 556?
And I hear that the 762x39 can punch through barriers better than the 556. Isnt that a really nice advantage?
My opinion of the 5.45 is that its basically like 5.56, only slightly worse in every way. One exception might be the fact that it has a tapered cartridge, which would make extraction easier.
You might know the saying how 'make things as simple as possible, but no simpler', there's a similar principle at work in cartridge design for small arms.
You want something that will reach out to the distances you need, and will penetrate the targets you intend, and and then you cut down as much as possible after that.
This is important since the major studies in small arms lethality have showed that volume of fire is the biggest correlation in casualty rates, and being able to carry a larger ammo supply also affords greater flexibility in small unit tactics (being able to keep up greater amounts of suppressing fire, for instance).
When it comes to the 7.62x39, the question is, are there any Barriers it can penetrate that 5.56x45 can't that are of the most common relevance? Well designed 5.56 rounds like TSX, SOST, or bonded SP can all penetrate common barriers like car doors, drywall, or wood siding. In any case, trying to hit an enemy through concealment is a rather niche application anyways.
My personal opinion for the best intermediate cartridge would be 6mm BR.
