I'm not gonna break into the physics of all this, but there's more to a pass through than speed. In fact, there are many instances where you will get better penetration from a slower arrow. Speed is only a part of the equation, arrow weight is the biggest factor. Light arrows slow down and lose energy faster. For deer sized game, it's a moot point. But if you're hunting bison, as in the above scenario.....I would take a 600 grain arrow flying 250 over a 350 grain arrow flying 310 any day of the week and twice on sunday.