Most marking on a turret are easily missed when you need to correct something. Because MOA and MRAD express angular corrections in different ways, the way you record distance, holdovers, and group movement for shots will be different for each unit. To make use of a good optic, you must use one angular language for all of your shooting, and mean what you say every time you click the turret, write a correction in a notebook, and call in a correction to a spotter.
Start with the angular language
Minute of Angle (MOA) divides a full circle into 64 segments of equal size, or 1/60 of a circle. Milliradian (MRAD) divides a full circle into 1000 equal parts, or 1/2000 of a circle. Neither MOA nor MRAD express bullet impact movement in relation to distance until that distance is mentioned.
Here is the most critical point many shooters misunderstand about reading a turret. A turret is an angular instrument and must be read as such. The angular movement of the reticle that you read off the turret must then be converted to a linear measurement based on the distance to the target.
Many anglers seem to feel that MOA is 'familiar' because the measurement of distance to a target and the size of a group are typically expressed in yards and inches. MRAD on the other hand seems to lend itself more to expressing distances and shot group sizes in meters and centimeters. This is a matter of personal preference however, and both systems can be used at any range, provided the unit of the turrets, the range to target, and the notes made for corrections are all consistently referenced.
Read the turret before touching it
Marks on the turret determine what angular language has been used. Note also that MOA and MRAD turrets are not always set to the same click value. Typically the click value is printed on the scope near the turret. Also note that in addition to the angular language the turret can also have a revolution indicator, zero stop and directional arrows. All these need to be noted and comprehended in order to zero the scope correctly.
Check three details:
– The unit that is printed on the turret (MOA or MRAD).
– The adjustment represented by one click.
– The direction in which the dial moves the point of impact.
A scope's turret click value should be a specified value which you verify against the manufacturer's manual, and against what is actually printed on the scope's turret. An otherwise familiar-appearing scope's turret does not necessarily mean it has the same click value as another's.
The above points are especially critical when replacing a rifle scope, borrowing a firearm from a friend to shoot it, or even transferring established "dope" to a new scope. Similar looking rifle scope turrets are not necessarily inter-changeable.
MOA and MRAD in the field
Both MOA and MRAD systems work well. The key factor is consistency. If your range card, your spotting scope, your ballistic computer, and your turret are all using the same angular unit, then you will find it very easy to hand off information. But if one person says shoot 4.25 MRAD of correction and the turret reads MOA, then that's a problem. You have to convert it.
MOA calculations can be quite easily applied at ranges recorded in inches and yards, whereas MRAD is much more straightforward when calculating in meters and centimeters. In addition, angular corrections can easily be expressed in decimal form when using MRAD.
This means to select the simplest system of measurement which matches your measurement units as well as those of other shooters such as spotter, range officers etc. With a little experience of a number of systems, one quickly realizes that the theoretically superior system can be a total nuisance in practice if it is not used correctly.
Keep scope zeroing separate from correction theory
Verify the adjustment system by making sure that the rifle and scope place shots near the chosen aiming point. Recheck initial zeros and verify your range-to-target distances and other observations. Verification shots at suitable ranges under safe conditions are always better than blindly accepting your corrections.
First, confirm the scope is properly mounted and the reticle is properly oriented for shooting. Record the initial zero, using the turret markings and the scope's click value as specified (printed on the scope tube, or in the scope's literature). Zeroing a scope involves making small changes to the scope's settings, and recording those changes.
Check to see what actually happened to the shot after the correction has been made and note this against the amount of turret movement that was made to achieve the correction. If the shot has moved in the opposite direction to that expected then check the arrows on the turret to ensure they are pointing in the correct direction. Also check the unit of measurement that has been selected for the turrets, the click value and your own hand written notes to ensure that everything is consistent. If any of these items are found to be incorrect then do not attempt to make further correction by adding more turret clicks.
Upon laying out your zeroing target, confusion will quickly be revealed. It might appear that your turret is working in one direction but not in the reverse. Upon closer inspection of your process for correlating your note to your turret's action, it will likely be revealed that a loose mounting, shaky shooting position, inconsistent ammunition, or even inaccurate aiming will all hide a simple mistake with a turret's marking.
Build notes that cannot be misread
Always write out the unit of measurement (e.g. 2.0 MRAD, 6 MOA) for every range note, as well as the unit of distance that you're using for the target(s). For example, 100m or 200yds. A simple number like '2' or '6' means nothing out of context.
Where multiple correction methods are used for a single card or sheet, it is best to stick to one method for notes. Where possible, record the original information, and the converted information for the turrets, to allow easy audit trailing of any errors that may have been made.
A useful range note must contain enough information for another to recreate the shot. The scope model, the turret unit, the click value, the zero range, the range to target, any notes on the environment, and the correction that was made all must be recorded. Simply recording the number to turret does not constitute sufficient notes.
Similarly, electronic shooters' logs and ballistic calculators need to have angular units set explicitly. Check that the calculated value and the turret display for the same value in the same units.
Choose the system your setup supports
This means choosing a scope zeroing system in relation to the entire setup (scope, rangefinder, shooting data, data sheets, switch communication etc.). While the dial is only one part of the system, the way distances are measured, target corrections communicated, shooting data recorded, and the type of reticle used in the scope all have to match the turret settings.
Matching the reticle markings to the turret settings makes sense in terms of easy holdover reference, but only if it is easy to read the reticle markings at the magnification and in the lighting conditions you shoot in. Some reticles are simpler to read than others.
The type of reticle also must support the scope and the application. A simple angular reference mark is better than a complex design. Also, simple marks are much easier to read than complex reticles at lower magnifications and at changing light conditions.
Your optic set up completes when you can explain to someone else the units, click value, zero measurement, and correction of direction for your scope setup. Simple clear written notes that are verified against your scope turret(s) are worth more than all the other optic selectors 'selling points'.
