Ok from what I understand SD (sectional density) is the density of a bullet compared to it's weight and length ! Is that correct ?
In other words you can have a 300 gr 375 bullet 18mm long and another 16 mm long also 300gr and the one that is 16mm long as more SD than the other.

Am I talking bull or am I on the right path ??? Then if it is so, does SD make a difference when hunting and why ? And what is the best SD to use and how do you measure SD of a bullet ???

Lots of questions but this has been bugging me for a while now.