“Dead nuts” is machinists’ jargon for nuts that have been torqued down until they will tighten no further. Or so I am told. When applied to zeroing a rifle, it means a default-to zero that you can refer to until the Clap of Doom.
A dead-nuts zero is not only important to competitive and tactical shooters, but also to hunters who have spent vast sums on equipment with which to pot unsuspecting animals at extreme distances and save themselves the work of stalking or being encumbered by old-fashioned concepts like fair chase.
Getting a dead-nuts zero means going out on an early morning when there’s no breeze and no mirage. You find out where your rifle shoots at whatever range you want to hunt at and adjust the scope accordingly. Simple, yes? Not in real life.
Let’s say you’re shooting a cartridge like the .308, which despite its modest size is effective at over 1,000 yards. Your first step is to get a dead-nuts zero for the shortest range at which you expect to clobber Bambi, let’s say 300 yards. (After that, you would be well advised to see where your bullets hit at 100 yards, just in case you get an old-fashioned close shot.)
Then, you’ll have to decide how you’ll handle longer ranges. You can buy a scope with stadia wires and use them, or you can put in clicks of elevation. Stadia wires are faster to use, but clicks are more accurate. However, in the heat of battle, you have to remember which stadia wire represents which distance, or you have to make sure you don’t turn the elevation knob Down when you mean it to go Up.