Winter is a great time to do the small, yet important things that are often overlooked during the shooting season. One of the most critical tests for your equipment you can perform is the scope box test.
Scopes, regardless of how much money you spent are the weakest link in our shooting system. We combine, the shooter, rifle, scope, and ammunition to make up this system. You can even expand this thinking to every accessory you are using, including the scope mounts, bipods, and magazines. Why is the scope the weakest link, it’s mechanical and often only tested in small batches back at the factory. Errors in scope adjustment are far more common than people realize too.
In today’s precision shooting economy, $1500 and less spent on a scope is considered the low end of the spectrum. Thanks to our training schedule we see a lot of different setups across a wide variety of optics. In other words, we have experience. It’s typical to see a 2% error factor in scopes at or below this price point. That has a cascading effect on the results one might see. Especially since these errors compound the farther out, you shoot. If you are using any ballistic software, this is your most significant point of failure when the curve does not easily line up. Testing your scope is just as crucial as zeroing your rifle.
Back in the day you’d flip open a magazine with a review of the latest and greatest optic being release for the new year. The reviewer would include a box test result, usually shot on an 8.5″ x11″ piece of paper. Complete waste of everyone’s time as that little box test does absolutely nothing. It’s just a return to zero test and not much else. See you need distance for the errors to appear, why because we are dealing with angles.
The more you adjust your scope, the farther the point of impact will move from the starting point. Because of this angle, we need for the errors to grow enough to be seen. Inside 400 yards it may never appear, but beyond 800 yards, now you have an issue. The farther you are shooting, the more precise you need to be, and this is where a lot of things fall apart.
Another point of error is TRUE MOA vs. Shooter MOA. We are talking the rounding error found in an MOA adjusted Optic. True MOA is 1.047″ at 100 yards. But Shooter MOA is 1″ at the same distance, it has been rounded down for simplicity. Compounding this 4.7% error over the distances we are shooting can mean as much as 17″ at 1000 yards. Most people will incorrectly say, “but Frank it’s only 10.47″ at 1000 yards, that .47″ is too small to notice.” Except we don’t use 1 MOA to shoot a 1000 yards, we use 30+ MOA to reach this range. Now times that error by 3+ and it grows to a miss.
I highly recommend you box test your optics across 100% of the useable travel. You want to perform the box test with a minimum of 24 inches of adjustment. That is as small as you want to build your tall target.
There are two methods of box testing people engage in:
Live Fire Test
They do the same thing, but one is subject to the system’s ability to accurately group the rifle. If you are typically shooting a 5/8th-inch group at 100 yards, that means you need the errors to be larger than your group size — one of the reasons why we use the Non-Live Fire method to test our scopes.
The Non-Firing Box test is easier to set up and perform with a few simple items. You need a tall target, something over 24″ in height. You want to use a level, I recommend at least a 4ft level, and then you need a Sharpie Marker. That is all that required to start, but we want to discuss this method in detail.
Back in the day, we used to have what we called Barber Poles on the range. A very tall, 4×4 post mounted vertically at 100 yards. The Barber Pole was painted white and black in an alternating pattern. Painting the 3.6″ segments allows the shooter to subtend the reticle and test its accuracy, but also they can run the reticle down the pole to determine the actual adjustment value. The tall target test is the same thing only portable. I highly recommend you set this up at home and then bring the target to the range. Two Uline Boards are easily 48 inches of space to work with.
Using the level and Sharpie you want to draw a straight line the maximum distance possible. Thirty-six inches is a great value to use because it’s ten mils with those scopes and 36 inches with an MOA scope. You need a starting point at the top of the target and a defined ending point at the bottom. I would highly recommend the optic being taken off the rifle and mounted as secure as possible. I designed an use a custom scope tracking tool that weighs 30LBS. We want it as heavy as possible, so the riflescope does not move when being adjusted. Many shooters have a spare mount that has been attached to a massive platform or I-Beam to stabilize the process.
Our Sniper’s Hide scope test tool is also used at the various military schoolhouses to test their scopes and help them mount them to the rings. We specifically donated these as part of our outreach to the military.
With the scope’s reticle placed at the top of the tall target for testing, the shooter will move the elevation up a set value, which will bring the reticle down. With the scope securely locked in place, you can also monitor the travel of the reticle to make sure it is not curving off the vertical line. You then compare the travel of the optic to the travel observed on paper. Did the scope track accurately across the entire adjustment range. Do this more than once to make sure you are not missing anything and be sure to adjust your parallax properly.
The curve often seen at the top of the elevation adjustment is due to the single spring holding the erector system against the turrets. The erector is a round tube, placed inside a round tube and managed with a single spring. As you dial up the spring will begin to trend to the side moving the erector system laterally as well as vertically.
A parallax error is a place where the offset can and will bite you. With the scope off the rifle, you will have a floating cheek weld. Keeping the reticle properly on target will require a perfectly adjusted parallax knob. Don’t overlook this step.
The firing method works too, you hold a central aiming point and adjust the scope up. By using the same aiming point and adjusting the scope turrets, the bullet impacts should track along with the line drawn on the target. It’s easier to do on most public ranges, but not as accurate because we include system errors: shooter error, movement off the platforms we, etc. You can also pick random points on the paper with the reticle, dial to them and make sure you impact where you dialed via the central aiming point. it’s a fun little drill to place random dots on the paper, read the reticle and then shoot for impact.
Make sure you have verified reference marks on the target. We also sell Sniper’s Hide Tall Targets at Box to Bench Precision. These are pre-made targets ready to shoot. Just staple them up, and you are good to go.
From the target to the turrets should be a perfect 100 yards. You can do meters, no issue there, but make sure the distance is correct. Public ranges are not always accurate so trust but verify when checking the range value. If you are off a little bit due to the range, you can fix it in the formulas. I use software to check my tracking, both ColdBore and Field Firing Solutions have utilities to do the work for you.
If you do discover an issue, and as I said, 2% is pretty standard. Not to worry, you can easily account of this in your software. A 2% error will be considered spec by the company, so don’t waste your time with customer service. If you go 5% or higher, I would recommend sending it in for a fix.
When I review any new scopes, I test tracking each trip to the range. It’s important to see if any changes appear. I can also follow along with my dope as the rifle and ammo combination should not change, only the optic I am using. If my data has consistently shown I need 7.2 Mils to reach a 1000 yards and now with the same rifle and ammo combination I need 7.4 Mils, the scope would be my first check.
There are a lot of factors we are looking at; the rings are one, don’t skimp on the rings. Those discount rings you bought are not doing you any favors. A scope will translate across platforms, the more you spend, the better your investment. We have seen a lot of problem with inexpensive vertically split rings. The scopes will track up and to the right, but coming back and going left are a big problem. The number of students with unnoticed errors cannot be overstated. The biggest issue with these rings is their inability to return to zero. They will dial out fine, but back they get hung up.
It’s no different than using a chronograph, zeroing your scope and turrets out, or grouping your lot of ammo. We want data, the better the records we keep, the more accurate we will be downrange. Dope, Data on Previous Engagement.
Here are the Sniper’s Hide Bullet Points for this month:
1. Tall Target Test your Scope regardless of cost
2. Use a minimum of 24 inches, 36 is better.
3. The Non-Firing Method is preferred.
4. Secure the scope, minimize any movement.
5. Record the values in your databook
6. Fix the errors in your software
Hope that gets you on the right track with scope testing. The more we know, the more comfortable we go. The beautiful part about doing this stuff over the winter breaks, no prone required. You spend a few great hours at the range without having to lay in the snow.