Re: scope for mk12 mod1
M5 will be nice because it matches the reticle.
However, if you haven't purchased it already yet, I suggest looking for a Nightforce 2.5-10x32 (or 24). They are incredibly light and IMO, better than the Leupold for a mk12mod1 build. I'd be patient and look for a used one on the for sale forum. My brother and I both have mk12mod1 clones, and he has a leupy 3.5-10 and i have the nightforce. While his FOV is better, the rifle weighs heavier with his monster of a scope.
Just a suggestion, good luck man and welcome to the mk12 club!