In this post we are going to be discussing how to properly zero a rifle by adjusting the scope on a precision rifle. It’s easy enough once you’ve done it but this can be daunting for newer shooters. For starters, let’s talk a little about the shooting aspect of zeroing a rifle. Obviously, you need to fire at a target, and adjust the scope so that by default the bullets land where the crosshairs are pointed at a given distance. What distance should you use though? If you want my opinion, 100 yards. Always 100 yards. Most drop tables and charts use a 100 yard zero but that isn’t the best reason to use that distance.
Zero a Rifle – What Distance?
If you zero a rifle at 100 yards your zero distance is sufficiently close so as to negate environmental differences in your shot. What I mean is, if you zero a rifle at 10 degrees, or 110 degrees, at 100 yards you are unlikely to see any significant movement in the placement of your shots at the zero range. Since you have no appreciable shift at 100 yards, if you dial to take a shot at say 600 or 800 yards your ballistic calculator or density altitude chart should have a valid firing solution for you despite the change in conditions. Conditions will always change and with a 100 yard zero you can account for those before you fire.
The problem comes in with long distance zeros. If you were to zero a rifle at say, 500 yards, on a 100 degree day and then you wanted to take a shot at 500 yards a few weeks later and the temperature was now 30 degrees, the environmental conditions become significant. You now have enough flight time for different environmental variables to affect the muzzle velocity and drag on the bullet which will shift the impact. If you tried to dial even farther than the zero the error would compound and you would wind up with an even larger offset. Brian Litz talks about this in his book, Accuracy and Precision for Long Range Shooting.
You want a stable zero.With modern scopes that have very plentiful ranges of travel you can be couple them with one piece mounts that add cant to the system. This will allow you to utilize even more of your scope’s available range of travel. As such, there really isn’t all that compelling a reason to use anything other than a 100 yard zero. Obviously different disciplines have different quirks so altering your zero may be necessary if you hunt at close ranges or you are shooting Extreme Long Distance, ELR, and with the mount you are using you are unable to achieve a 100 yard zero. For the vast majority of shooters though, 100 yards is sufficient.
Tricks to Zero a Rifle
My recommendation is that you find the mechanical center of your scope’s travel for elevation and windage prior to trying to zero a rifle. Turn the turret in one direction until it stops, then turn it back the other way and count the number of turns you are able to achieve, then divide that number by two. Say you wind up with 16.8 Mils of travel…the center would be 8.4. Set the elevation turret there and leave it. Repeat the procedure for your windage turret. The reason is so that when you begin to fire live ammunition through the rifle you are only dealing with the offset between the scope and the bore. If the turrets are spun all over it will take you longer to figure out where you are hitting in the first place and walk the shots in to a reliable and repeatable zero.
I would now suggest you first fire at a distance of 50 yards and get your windage down pat. Fire two rounds before making adjustments. The reason I say this is we aren’t all as consistent and awesome shooters as we like to believe. You don’t have to admit that to your friends but at least admit it to yourself. Fire two rounds and if they stack on top or near each other you know you aren’t jerking the gun or messing up your fundamentals too badly. Adjust the turrets on the scope so that you can put two rounds on the center line of the bulls eye. Don’t worry about the elevation just yet, if its above or below the bulls eye that’s fine but make sure the gun is stacking shots directly on top of the center line.
Now move back to 100 yards and set the elevation so the impacts go through the bulls eye. I would suggest you leave the windage alone unless you are really seeing a very consistent issue with regard to your point of impact to one side or the other of the bulls eye. You zeroed the windage at 50 yards and that isn’t time enough for anything but shooter error to affect the placement of the shot, the same is true of 100 yards. So if you had them on the center line at 50 and now they are way off the problem might be the shooter and not the rifle. If you need to adjust the windage, you can, just keep what I’m saying in mind.
When you have finished you should be able to get rounds on the bulls eye repeatably and reliably. This isn’t always easy and I suggest you use a 1 Inch pasted target to shoot at. If you miss it consistently even after zeroing you might have an issue with the setup of your rifle or one of the fundamentals of marksmanship. If you are having problems I suggest you let a more experienced shooter try your rifle before making any changes. Plenty of factory rifles have issues straight from the box but you want to make sure the gun has a problem before you start fixing something that may not be broken. That’s why I suggest you have a more experienced shooter try your rifle if you are having problems.