MOA - Minute of Angle & MilRAD
Aminute of arc (MOA - known as minute of angle in shooting circles), arcminute, or minute arc, is a unit of angular measurement equal to 1/60 of one degree.
Shooting Units: MOA Minute of Angle
In shooting circles, Minute of Angle, or MOA represents approximately one inch at 100 yards (it's actually 1.047 inches, but screw that for calculating in your head!)
Many modern rifle scopes are set up to adjust in half or quarter MOA increments, also know as clicks. Therefore, if you know the distance of the target (100 yards) and your point of impact is 33 high and 1.53 of where youintended the shot to go, then you need to adjust your scope 3 MOA down, and 1.5 MOA right. This makes adjustments on the scope easy, enabling you to quickly dial in the scope to your intended point of impact.
It is worth noting, that scopes can actually be calibrated in true MOA, or in Shooters MOA (SMOA) which is a true 1 inch at 100 yards. While this may not make a whole lot of differnce at shorter ranges at longer ranges the differencecompounds if adjusting over 20 MOA, this could add up to over an inch difference. Significant if you are looking for a first shot hit.
Firearm accuracy
Manufacturers will often express the accuracy of their firearm in MOA. For example, a 1 MOA rifle should be capable, under ideal conditions, of shooting an average 1-inch groups at 100 yards. This discounts shooter error andoften also defines a specific ammunition that needs to be used. It also often only refers to a group of 3 to 5 shots. It is often suggested that larger groups should be used in order to measure this. Many modern rifles are capable of sub-moa grouping it has become the defacto standard formarketing a precision rifle.
But we live in a metric world
True. Though many people have adapted to the MOA standard, another system, the MilRad lives in the metric world. A MilRad is equal to one 1000th of the target range. This is laid out in a circle around the shooters position, with thetarget range as the radius. Which means, 2 x pi x 1000. Therefore 1 MOA = 0.2908 MilRad. Adjusting one Milrad up at 100 meters will result in an offset of 100 mm. The markings on a reticle that mark MilRads are called MilDots. Such a reticle is called aMilDot Reticle.
Mixed systems
What is most important is that no matter what system you decide to use, is ensuring that the reticle measurements (if it has them) and your turret adjustments are the same. For example, if your reticle gives measurements in MOA, dontget turrets with MilRad adjustments. You are just asking for confusion. If you are mathematically inclined, go for it but converting from imperial to metric while estimating wind and range and hoping the animal doesnt wander off could be a bit much. Why a manufacturer even allows you topurchase them this way I am not sure. But it is possible, so pay attention when purchasing.
What system should I use?
Depends. While MOA is inherently has finer adjustments what MilRAD it makes sense to stick with what system you are already familiar with. I.e. if you were to estimate a distance to an object, would it be in meters or feet? What doyour shooting buddies already shoot? It might make sense to keep it the same so you can easily communicate back and forth. Already own a rangefinder? What is it set up to return information in? By keeping the system the same you reduce the amount of conversion you have to do.