fulll size vs. collet

[Jack]

I think you're looking at the Lee collet neck sizer- which sizes just the neck.
You'll get different opinions about whether you need to full length size cases after they've been fired in your rifle.
My opinion is that you'll end up wanting to full length size at some point, if not every time, so you'll end up buying a full length sizing die. For game hunting, getting the last tiny bit of accuracy isn't really needed- but perfect functioning is. For that reason, full length sizing is often the way to go on game loads.
There are so many factors involved, it's difficult to give an ironclad yes or no answer.