When you open up that Christmas present and find a brand-new scope for your rifle, what is your first thought?

If you’re like most of us, you just bolt it on the top of your rifle and head to the range to run round after round through the barrel while zeroing in the reticles.

But Gonzales gunsmith and former Marine Larry Townsend Sr. said that’s absolutely the wrong way to go about sighting in a new scope.

“What most people do is just mount the scope on the gun and then zero the scope by moving, say, 15 clicks right,” Townsend said. “But what that does is moves (the reticles) so far out of the sweet spot on the scope that … at 200 and 300 yards, you’re missing the target, and you don’t know why.

“All the scopes have a sweet spot, and if you get (the reticles) too far off the sweet spot, the farther out you go, the farther off it’s going to be.”

And by just slapping the scope onto a rifle and then zeroing in the reticles, you’re almost guaranteeing there will be downrange problems.

To zero a scope properly simply takes the extra step of using a handheld mirror to determine if the front and rear reticles are in matching positions.

“If you take your scope and put a mirror right in front of it — a little hand mirror, right in front of it — and look through it, both of the reticles should match up to show one reticle,” Townsend said. “What that tells you is ... when you only see one reticle, it’s in the sweet spot of the scope itself.

“At that point, what you do is you then mount the scope to the gun. Once it’s centered, it shouldn’t be more than five clicks off either way.”

So instead of taking a box of rounds to get zeroed in at 100 yards — and risking longer shots going astray — you only need to fire a round or two.

And you can be more confident when that big buck steps out at 300 yards.