As shooters we are all a bit obsessed with accuracy and precision. Especially rifle shooters. Likely, everyone has seen the Col. Townsend Whelen quote: “only accurate rifles are interesting” at some point in their reading and research.
In order to achieve the best accuracy from our rifle we need to be sure we have our scope properly zeroed.
The absolute first step is to make sure your scope is properly mounted and absolutely square to the rifle. I see a lot of shooters who will purchase a package with the scope included and already mounted to the gun. I would highly recommend that you take the time to remove the scope and mounts, be sure they are properly cleaned and then remount the scope yourself using correct tools and proper torque values for the base and rings you are using.
Mounting a scope is simple and something every rifle shooter can learn to do properly very quickly.
Tools and Equipment
To properly zero your scope you need a few basic items at the range.
First up is a sturdy bench and front rifle rest or sandbags. You will also need a rear rifle bag to stabilize the butt of the rifle. If you don’t have a bench available you can shoot prone from sandbags or a properly mounted bipod.
You need a range that will allow you to set up a target at 25 yards and 100 yards. For the targets use something large and easily visible at 100 yards, like a 20”x20” square. The targets should have a grid pattern so you can line up the reticle in your scope absolutely vertical to the target.
A plumb bob or level is handy to make sure your targets and the grids on them are absolutely level.
Be sure you have the instructions for your scope so you know how to make adjustments and what happens with each click of the turret.
Focus the Eyepiece
The rear eyepiece housing is used to focus the reticle for your eyes. Simply turn the eyepiece all the way to the left or right. The reticle will likely be out of focus. Now, start turning the eyepiece until the reticle comes in to sharp focus. If there is a locking feature, lock it down once the focus is correct for you.
This seems like some mystical procedure, but it is really nothing more than making sure the centerline of the bore and scope reticle are pointing at the same spot at a given distance.
To align the bore with your 100 yard target, remove the bolt or take the upper off your AR-platform and remove the charging handle and bolt carrier group.
Next, set up the rifle using sandbags or a front rest and rear bag while looking down the barrel from the breech. Anchor the rifle in place once the bore is centered on the center of the target.
Now look through the scope. Is the reticle centered on the center of the target as well? If not, turn the elevation and windage turrets until the reticle is centered on the target. It helps to have another person hold the rifle steady as you make adjustments. Double check your view through the bore to make sure the rifle did not move as you dialed in the scope.
Once the bore and reticle are centered on the same point your rifle is bore sighted.
If you are shooting a rifle such as a lever action or semi-automatic that does not allow sighting down the bore, fire your first shots at 25 yards to get the rough adjustments made before you attempt to shoot at a longer distance. You can also use a laser bore sighter to dial in the initial adjustments.
This initial bore sighting exercise is necessary because sometimes our mounting system is not perfectly square or the holes in the rifle are not absolutely true to the center line of the bore. This will cause the scope to point somewhere other than where the barrel is pointing.
Even if you have bore sighted the rifle, make your first shots on paper at 25 yards. This close range work eliminates error that shooting at a longer range can magnify. It also should mean all your shots will at least hit the target someplace.
Holding the vertical wire of the reticle directly on a vertical grid line on the target will insure the gun is absolutely level. Fire your first shot.
After the recoil, place the reticle back on the spot you held on when you fired the shot.
You should be able to see your bullet hole. Now, without moving the rifle turn the turrets until the reticle is centered on the bullet hole.
Fire your next shot holding on the same exact spot on your target. Check your bullet hole. If the impact is not where it needs to be adjust the turrets again to bring the reticle to the center of the bullet hole.
Fire your next shot. You should now be very close to the point you are holding when you shoot the rifle.
Shoot a 3-round group. See where your group is in relation to the reticle center hold. You should have a nice tight group right where you are holding. It is time to move out to 100 yards to fine tune your zero.
Adjustments Along the Way
Up to this point you have not had to count any clicks or figure out how many inches you need to move the group to be in the center of your hold. You have simply adjusted the scope to match your center of impact and zeroed the scope and centerline of the bore.
Know Your Click Values
Be sure you know what happens with each click before you start you final shooting at 100 yards. On many of today’s scopes the click value will be engraved on the turrets or inside the turret caps. For example, “1 Click = ¼ MOA”. This means that each click on the turret will move the point of impact approximately 1/4” at 100 yards. So if the group is 2 inches low, 8 clicks up will be required to bring the group to the center of the hold.
Some scopes will have ½ MOA adjustments. Some scopes will be calibrated to move in MILS.
MOA’s and MILS – What’s it Mean?
Check out MOA vs. Mills in an earlier Gander Outdoors post.
MOA or Minute of Angle is a unit of angular measurement.
1 MOA is 1/60th of a degree.
At 100 yards, 1 MOA is about 1 inch. The actual measurement is 1.047 inches.
So for every 100 yards the MOA increases by 1 inch. For instance, 1 MOA at 300 yards is 3 inches.
4 MOA at 200 yards would be 8 inches.
MILS or milliradians are a measurement dividing the radians in a circle. There are 1000 milliradians in one radian.
1 mil at 100 yards is 10 centimeters or 3.6 inches.
To make it really simple, 1 mil equals 1 yard at a 100 yards or 1 meter at 1000 meters.
Scopes that are marked in mils are usually calibrated in 1/10 mil increments. Each click is .36 inches. Each full mil is 3.6 inches at 100 yards.
For the most part, the scopes you will find on the shelf will be MOA adjustable scopes. Many will have a reticle with hash marks or dots that allow for holdover or windage corrections. Be sure to check the information that comes with your scope. Although the turrets may be calibrated in MOA, many reticles are mil graduations. It may not be super critical at 300 yards but think about what that holdover is at 1000 yards.
If you hold two dots over at 1000 yards with an MOA reticle, that equates to a 21 inch high hold.
That same two dot holdover with a mil reticle equates to 72 inches. You will shoot over the target.
Case in point. Last year shooting a Ruger American Predator rifle in 6.5 Creedmoor I zeroed my scope at 430 yards. I then proceeded to dial in my elevation for 620 yards, 700 yards, 830 yards and then 1000 yards. The scope ran out of vertical adjustment. I figured my hold needed to be one and half dots to make the 1000 yard shot. I did not realize that the scope had a mil reticle. I fired my shot…right over the steel. Instead of roughly 15 inches of additional vertical I was holding about 54 inches. The moral of the story, understand and know how to use the equipment you have.
Zero Stop Turrets
At one time a scope with a zero stop was only found on very high-end, long-range, and military-style scopes. Today, more and more scopes come standard with zero stops for ease of use in the field.
Quite simply, once you have your rifle zeroed at 100 yards you can set the turrets on both the elevation and windage adjustments back to zero.
This means anytime you use the turrets to dial a longer range or compensate for wind you do not have to remember how many clicks you made from your original setting. When you are done shooting at that range simply dial the turret back until it stops and you know you are now zeroed again at 100 yards.
Confirming Your Scope Adjustments
A simple test to see how precise and how repeatable your scope adjustments are can be done by “shooting the box”.
Once you are zeroed at 100 yards and have your turrets reset, dial your windage to hit 6 inches left. So on your ¼ MOA dial, that means 6 MOA or 24 clicks. Fire a shot.
Now, dial up 6 MOA and fire another shot. Dial 12 MOA right and fire a shot. Dial 6 MOA down and fire shot. Finally dial 6 MOA left and fire your final shot. You should hit the center of the target again, and you should have a nice square pattern of bullet holes if you are shooting carefully.
Be sure when you shoot the box your are holding on the center of the target for every shot.
This exercise will show you how close your scope tracks to the specs stated for the adjustment turrets.
Stretching It Out – Shooting at Longer Ranges
With your scope zeroed at 100 yards and your turrets locked in, it’s time to bang some steel at longer ranges.
You can make a simple drop chart by studying the trajectory tables for the bullets you are using in any reloading manual. Or you can make one by using the free calculators at JBM Ballistics.
The chart below was calculated using the JBM calculator for a .223 and with the average environmental conditions at a range near our home.
The drop chart simply tells you how much your bullet drops at a given distance with a given starting muzzle velocity. If you have configured the calculator for MOA, you know exactly what you need to dial in or how much to hold over to make a hit at your chosen distance.
If you have a chronograph you plug in exactly how fast your bullet is moving on average. If not, use the data on the cartridge box. If your shots are going high based on the drop table for a given range, your velocity is likely a bit higher and you need to refigure your drops for the higher velocity. If you are consistently low, your velocity is probably lower than stated.
Col. Whelen was right. Having an accurate rifle is both interesting and fun.
Learning to zero your scope and use its features will lead to many happy days at the range and hits on targets you may not have thought possible.