OK, I understand the principle of an MOA mount, it gives you a degree of built-in elevation.

But when do you decide to use such a mount?

I've got a .308 coming. What's it's useful range? My scope is a Bushnell 3200 3-9x40. With a zero base, what's my max range?

Basically, what I'm asking is as a noob, should I stay with a zero, will I be pleasantly surprised with 10? Is 20 only for 1000 yard big boys?