The long and the short of it is that mil and FFP are the standard for tactical scopes. MOA FFP scopes were only created due to consumer demand, by consumers that don't know how to use an FFP scope. They wanted MOA because they incorrectly relate it to inches and incorrectly assume that they need to use the metric system with a mil scope. 99% of knowledgeable users all go with mil. It's pretty apparent when you look at the Precision Rifle Series Stats.
There is no standardization with MOA. Some scopes that are marked MOA are really IPHY. Some have an MOA reticle with IPHY turrets. And, there is no standardization in MOA reticles. Some have 1 MOA major ticks, some have 2 MOA major ticks, some have 3 MOA major ticks, others have 5 MOA major ticks. MOA is a broken system that has no advantage whatsoever in a tactical scope. Mil reticles will always have 1 mil major ticks in high power scopes.
MOA and IPHY are two different units. MOA is 1.047" at 100 yards, not 1". Small difference right? Well, you're not dialing 1 MOA to get to 1000 yards, your dialing more like 40 MOA, and that 0.047" difference gets multiplied by 40, and that gets multiplied again by 10.
40 MOA @ 1000 yards = 40 x 1.047" x 10 = 418.8"
40 IPHY @ 1000 yards = 40 x 1" x 10 = 400"
People shooting on square ranges ignore the difference. They can because they're shooting at an 8' target board, have sighting shots and have someone putting big orange dots where their bullet hits. If you're doing any kind of practical shooting (hunting or a tactical match), those first two shots are going to be your only shots. Mix up MOA and IPHY in your ballistic calculator and that's a miss. Because you're not firing enough shots to center a group, the finer MOA adjustment vs. mil is meaningless.
Thinking about things in inches or cm and relating them to the size of your target is a technique that is used on square ranges. It's a very poor technique to use in field/tactical shooting where distances aren't evenly divisible by 100 (they are often not known with certainty) and targets aren't scaled so that the math works out nicely. If the target isn't the size you think it is (in real life it seldom is), your estimated size of the miss is going to be wrong. And if you ranged the target with your reticle, your range will also be wrong because the target size you used to calculate it was wrong (it can also be wrong with a rangefinder if you picked up something in front or in back of your target instead of your target). So, you're calculating a correction using an incorrect estimate of the miss and/or an incorrect distance. And you stand a good chance of messing up the math, especially under stress. The reticle will accurately tell you what the miss is even if you got the ranging wrong. It doesn't care about the target's size or its shape or what distance it's at. Doesn't matter what the distance is.
There is no reason to ever think about how big your click is with an FFP scope. Someone who teaches this doesn't know how to use an FFP scope. The mil in your reticle is the same as the mil on the turrets. Whatever you measure with your reticle can be put directly into your turrets and whatever you dial on your turret can be held over/off with the reticle.
1 mil = 1 mil at 100 yards
1 mil = 1 mil at 200 yards
1 mil = 1 mil at 300 yards
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1 mil = 1 mil at 1000 yards
Its an angle, it corrects itself for distance. The reticle is a ruler that is right in front of your nose that is in the same units as your turret. How many inches or cm your click is doesn't matter. People who know how to use an FFP scope NEVER need to think about how big their click is at whatever distance. It's irrelevant. They don't think about it, they just measure with the reticle. It's MORE accurate than thinking about inches and doing math.
There is also the fact that things like leads on movers have constant mil values, but a different inch values for each distance. You hold the same mil value for a 3 MPH target at 156 yards as you do for a 3MPH target at 439 yards. The inch leads will be different at every distance, even for targets of the same speed.
