As the MK12 comes sans sights, I chose what I thought to be the proper optic for its intended application. Leupold was kind enough to provide me with an MK4 MR/T, or "medium range tactical" scope. My example was the 2.5-8 x 36 with an illuminated tactical milling reticle (TMR). If you're not familiar with the TMR, the concept is actually quite simple, assuming you're familiar with the concept of ranging with milliradians (MILS.) The TMR takes that concept and makes it a bit simpler, using hash marks to break down mils into 0.2 subsections. Same idea, just more accurate. Throw in the broad range of magnification and multiple illumination levels, and this scope offers amazing adjustability. For a medium range rifle designed to not only be precise but also have the ability to quickly engage multiple targets if necessary, an easy-to-read optic is a huge benefit.
To mount the Leupold to the MK12, I chose Mark LaRue's one-piece scope mount, the SPR/M4 LT-104. Of all the optic mounts I've tested, LaRue's have been the only ones to live up to the claim of true repeatability, or the ability to retain zero after being removed and re-mounted to the receiver. Once the Leupold was properly torqued into the LT104 and mounted to the MK12 I was ready to make some noise.
Rounds Downrange
The MK12's rifle-length gas system and longer 18-inch barrel would tend to favor a heavier bullet, yet the faster 1:7 twist would allow a lighter bullet to properly stabilize and could be very handy in closer range. So to test the rifle's versatility, I grabbed a box of every match grade .223 ammo I had in my safe, including Black Hills 52-grain Match BTHP, Federal TRU 55-grain Sierra BTHP, HPR Hyper Clean 60-grain VMAX, and HPR Hyper Clean 75-grain Match BTHP.
I zeroed the MK12 at 50 yards with the Federal 55-grain BTHP. This is currently what my agency carries as a duty round, both for the SWAT team and patrol rifles, and we're continuously impressed with its performance. The quality of the Leupold scope and LaRue mount came in handy here as I was only about 2 MOA high and left during my first group.