The discussion was mostly generalized from what I could gather and was specifically stating that for the 45-70, anything over ~1600FPS you would start to see less penetration from projectiles in the 400+gr. In other words, diminishing returns the higher the velocity. I understand that deformation of the bullet and other bullet "failures" would potentially cause penetration issues such as bullet path changes and deflection but I would think that at this point it would be more related to bullet construction/design than MV given the bullet is capable of achieving said velocities and you are not "over clocking" it as it were. I would agree with Ernie that given the relatively short distances of handgun hunting, MV is acceptable for calculation and that under say 100yards, look for a bullet that performs with in that limited velocity range. Thanks for the input folks. Very much appreciated. Looks like I have some tests to run