The glass is very clear, I had a student out with one a few weeks ago. But! I hate the fact that they are Mil retocle, MOA turret. You get your windage in Mils since 99% of the time you hold wind and dial elevation. So what has to happen is input BC, MV, bullet diameter and weight, the calculator gives you all the data you need, Mils and MOA. Shoot the range, and if you see miss or impact low or high (in Mils) you have to convert to MOA so that you can fix the elevation problem on the turret which speaks in MOA.
I illustrate it like this; you're cutting in base board in your livingroom. You measure four walls with a tape measure in inches, you set that tape measure down and walk outside to the miter saw and pick up a tape measure in centimeters. You have to do a conversion to make the measurements equal each other. Why not use the same unit of measurement for both? So if you see a correction needed in Mils, reach up and correct it on the turret in Mils. Then once you get DOPE all the way down the range, recording as you go, you can go back into the calculator and true up the DOPE to match what the calculator gives you for future corrections. Very important if you plan to shoot something farther than you have before, and very important so that you can lean on the calculator for the various environmental changes that will effect bullet flight. It WILL NOT fly the same today as it will in the summer weather, and/ or at various elevations from sea level.
That leads me to the problem I have with second focal plane. In that summer weather I mentioned, it is advantagous to be able to dial down the magnification and a Mil still be a Mil. The higher the ambiant temp, the worse the mirage is, the more you want to dial down elevation. If you have FFP then your wind holds (in Mils) are still correct.
So no, I am not a big fan of the Mark 4. Nor am I a fan, at all, of the BDC type turrets or reticles. The corrections are not set in stone and you need to be able to adjust as needed.
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