Hi, I've been working for a long time on a ballistics model to be used in a game. I have read quite a bit of material from material science to fluid dynamics to ballistics. I am by no means an expert, and have only rudimentary knowledge in most areas. I am very close to finishing steady state and impact state ballistics, somewhat equivalent to what is more commonly known as external and terminal ballistics. However, I still have not finished the model for bullet deformation. The accuracy need not be great, and simple approximations are enough for my real-time purposes, so I've decided on the two following attributes: deformation onset (m) deformation rate (1/m/Pa) Deformation onset is the neck of the permanent cavity, and deformation rate is simply the difference in length of a rod over a specific distance at a specific stress. The follwing site gives me some ballistic cavitation profiles for various bullet (and there are probably plenty more sites), that I can use to approximate the behaviour of a bullet. However, this is in flesh, and does not account for how a bullet would behave in a different material, e.g. wood, concrete, or steel. (1) Terminal Ballistics The average shear strength of flesh is 0.4 MPa, and a specific structural steel 145 MPa, that's a huge difference. I would expect most soft bullet to shatter in a high velocity impact with steel, but how quick is the rate of change in deformation onset? If a 5.45x39 mm Russian bullet has a deformation onset of 7 cm in flesh, as I increase the stress, how quickly would the deformation onset decrease? Would it decrease at all? Deformation rate is how quickly the bullet deforms once it has reached the onset point. Does anyone have any material that would help me with this issue? Does anyone have any practical experience with how bullets deform with different materials? Any help will be very much appreciated! EDIT: two early guesses is that it is either linear, or that it is mostly dependent on dynamic stress and thus sqared term.