How Effective is the MK12?

[TehLlama]

My point is, there is no round available (that i'm aware of) that allows you to quietly and effectively engage targets at 600+ meters.

Back to the topic, the closest thing to doing exactly that is the Mk12, and that's why its use seems to have gone well beyond what a lot of people would have expected out of a light precision rifle - it was the quietest available to our squad sized patrols, had the most optics and effective range for the same role, and it's light/compact enough that that guy doesn't require another weapon system for MOUT/compound clearing/other nonsense. At distance 'quiet' and 'effective' are relative, putting a round on target anywhere against an unarmored jackass in a mandress is going to put that guy out of the fight for a while and dissuade his stupid buddies from emplacing IEDs in the same spot, being able to do so without completely telegraphing the location of an overwatch team is fantastic. A lot of the value of the Mk12 is that they became a squad or even fireteam level asset (which is why the STANAG magwell became so important), so a lot of the inherent limitations of that platform were at least mitigated by having more of them at the sharp end (meaning that the benefits went out with every patrol).

For my part, I was so enamored with the concept that I wound up with two SPR-format uppers (a CMMG M18 and Centurion Mk12 barreled upper with Leupold TS30A2). I have since started to work on a slightly more compact variant of that setup for my personal uses, and after a couple iterations I've wound up with a 16" High Caliber Sales Recce upper with an OPS 14th can - basically trimming 4" off the front in equal parts of suppressor and barrel, while running a more modernized KAC (URX3.1) handguard. My particular example is in that blurred line range of Recce Rifle more than Mk12, but if another contract went out for the same effective treatment of updating the Mk11/M110 to the M110-C then I think a rifle nearly identical to mine is what the result would be. This setup likely gives up some terminal performance, but given the sort of results MarkM and Pappabear are getting out of similar 16" uppers and Mk262-esque handloads I really think it would be a passable answer for a .civ application of a squad DM.