>amerimutt ignores logic, reason and laws of physics because it conflicts with his pre-existing opinion
Why am I not surprised.
Slowing in dense medium is a factor of square of speed. Having twice the weight doesn't produce nearly as much stopping distance as having twice the speed.
>inb4 hurr durr overpenetration
All that shit ties to energy, dipshit.
Breakage reduces penetration for the same reason expansion does: increase in surface area to energy ratio. Small projectiles have poor penetration not because they're light, but because they're not very energetic in relation to their impact cross section. Hence why sabots are a thing - a projectile far lighter than ordinary, with far greater penetration than ordinary, all due to small cross section compared to the energy it carries.
I get your angle that "physics don't mean shit we've got practical evidence" but the evidence conforms to the physics which you just don't grasp that well, and the entire subject revolves around nothing but physics.
My brother of african descent, you don't even know what is kinetic and potential energy and what's the difference between them, you're not in any fucking position to argue physics, you would however benefit from reading a book.
It's the same for penetrating tissue, because tissue is a solid object. With huge elasticity and tiny shear modulus and ultimate tensile strength, but a solid nonetheless. As opposed to a liquid, which readily moves out of the way of a penetrator and immediately rejoins into a bulk material after it passes. And with gases you can basically work with idealized versions of equations. Also, sabot basically a design of nearly every AP bullet in existence - tiny steel core in a lead shell. The idea being that the lead shell is shed as it is stopped by the armor because of its size, the steel rod will continue moving with less impedance. The lead shell is kept because 2 mm rod penetrator doesn't exactly makes grievous wounds, and being specifically designed to maximize penetration, it just zips right through the body.
Wait nevermind, a lot of designs just wrap a steel rod with copper jacket and pad it with a bit of lead to give it more of a ballistic shape. I guess you don't really need to make a small radius penetrator unless you're trying to defeat level 6 armor, in which case good fucking luck anyway.