Riflescopes: Elevation Adjustment
Adjustments on a riflescope are commonly made by turning or “dialing” a turret (the knob on top and side of your riflescope). When dialing a turret, an audible and tactile click is made indicating that an adjustment has been made. Each click changes the angle in which light is being reflected by moving parts inside the scope. By changing the angle of the light, the reticle appears to shift up or down, giving the shooter room to adjust to the point of impact.
There are a myriad of ways to tweak and optimize elevation adjustments on a rifle, but one thing that you can’t do is change the adjustment range of your riflescope. The number of clicks you get on your windage and elevation turrets will remain the same regardless of the scope base, rings, or optic accessories added to the rifle. If a riflescope has 100 MOA of elevation adjustment and is mounted to a 20 MOA base, you still only have 100 MOA of adjustment in the scope – you’ve just dropped the angle of the riflescope itself by 20 MOA to get more functional use out of the 100 MOA adjustment range in the scope.
So what does all this mean and why does it matter?
The amount of adjustment in the elevation turret is particularly important when shooting at greater distances or when changing between supersonic and subsonic ammunition like one might do with a rifle chambered in the popular 300 BLK cartridge. If you know your cartridge will have a significant amount of drop at the distance you intend to shoot, you will want enough adjustment in your elevation turret to compensate for that drop. Understanding how much drop you will encounter will depend on a number of factors, the primary factor being the cartridge.
On average, a rifle chambered in .308 Winchester firing a 178 grain bullet out of a 24” barrel zeroed at 200 yards will drop 50.9” at 500 yards, roughly 9.7 MOA of elevation adjustment. With the exact same bullet, barrel length, and zero, a rifle chambered in .300 Winchester Magnum will drop only 37.6”, or a roughly 7.2 MOA adjustment. As shooting distances push beyond 500 yards, the bullet drop will increase for both cartridges and demand even greater range of adjustment from the elevation turret. The significant difference in bullet drop between these cartridges can be attributed to their different muzzle velocities.
For the most part, faster muzzle velocities correspond to flatter trajectories and less bullet drop to a certain point. With less bullet drop, less elevation adjustment is needed to dial your reticle back to your bullet’s point of impact. Of course, bullets don’t fly forever and every cartridge will exhibit significant bullet drop at some distance. The point then, is to figure out for yourself what that distance will be for your particular rifle and what distance you’re capable of making accurate shots to.
The best way to figure this out is to chronograph your rifle with the ammunition you intend to use on a hunt or in a competition, then input that data into a ballistic calculator. There are a variety of different ballistic calculator apps for mobile phones available for cheap or free, so if you’re just starting out, download a free one and get started. A quick search online will also reveal a number of free calculators available in website form. Every app is different, but the key information most ask for is as follows:
- Muzzle Velocity
- Zero Distance
- BC or Ballistic Coefficient (Be sure you put the G7 in the G7 box or G1 in the G1 box)
Some manufacturers offer BC and muzzle velocity averages printed on the box or listed on their website, so if you are unable to borrow a chronograph, this data should suffice until you decide to get competitive.
BDC Reticles vs Custom Turrets
A Bullet Drop Compensating reticle, or BDC reticle, is usually comprised of a matrix of etchings used to represent given measurements at varying distances, allowing the shooter to make his or her adjustments “in the scope” by placing the appropriate hash marks over the target – this is called a holdover. BDC reticles, have a tendency to be very “busy” visually and can be intimidating for new shooters, but they are extremely efficient with practice.
By contrast, custom turrets are made to simplify elevation adjustments made with the turret as opposed to “in the scope” like BDC reticles. This is accomplished by etching 200 yard, 300 yard, 500 yard, and so on into the turret using data for a specific rifle and cartridge combination.
Custom turrets are also extremely efficient, and generally require less practice and training to use effectively.
For example, if we know a rifle is zeroed at 200 yards and the bullet will drop 50.9” at 500 yards, the turret will be etched with a “500” mark at the roughly 9.7 MOA elevation adjustment. Elevation turrets are commonly built with .25 MOA clicks, meaning each click will adjust the reticle either up or down by .25 MOA. With a .25 MOA turret, our 9.7 MOA adjustment equates to about 39 clicks (which would actually be a 9.75 MOA adjustment). Rather than counting out 39 clicks, a custom turret is etched or otherwise marked to indicate the adjustment for that distance.
Build quality is extremely important for both reticles and custom turrets alike, as shotty manufacturing practices will make themselves known when shooting for precision. If a manufacturer advertises .25 MOA or .1 Mil turrets, these adjustments should be exact throughout the full range of adjustment on the turret. Lower quality optics may not actually make adjustments as precisely as higher quality optics, and this becomes evident when performing “tracking” tests. A riflescope with 100 MOA of elevation adjustment (50 up and 50 down) and .25 MOA clicks should adjust 52.35” up and 52.35” down at 100 yards. To avoid finding a target large enough to test this at 100 yards, tracking can be tested at shorter distances like 25 to 50 yards.Since it’s difficult to perform a tracking test on a riflescope you don’t own, in-depth reviews can be found online and in publications like Western Hunter Magazine where these tests are performed by subject-matter experts who give honest feedback on how the optics performed. These reviews are a great resource to get as much information as possible before making a riflescope purchase. Talking to someone on our team is always an option as well. If you’re interested in performing your own tracking test, National Shooting Sports Foundation has a great video that outlines exactly how this is done. Similar tests can be performed with a BDC reticle to ensure each mark is etched accurately.