Re: lepold mk4??
You should look at a mil on mil first focal plane. The leupolds m5 (5mil per rev ) turrets look pretty good and they have several different power ranges with first focal plane ( reticle stays the same size in relation to the target at all power ranges ).
They are around $1600 I believe.
In my opinion, the Nightforce F1 is a much better option. It has a better reticle (MLR-2), has an illuminated reticle, 10 mils per revolution, has a zero stop, has constant eye relief at all power ranges ( the leupolds eye relief changes quite a bit when you go from high power to lower power zoom, on low power you will be craning your head way back). The only thing the Leupold has over the Nightforce F 1 is that it is available in higher powered versions (6.5-20 ).
The Nightforce is around $2300 and comes with a $150 set of rings(which you can sell if you already have a good set of rings). They can be had used for around $1950 +/-.
The Leupy is a good scope, the Nightforce just offers so much more and I think a NF holds it's value much better. For just a little more $$$, I would much rather have a slightly used F1 than a new Leupold ffp m5.