Scroll down to Attachment 0008 PHASE I EVALUATION CRITERIA for the details:
Weight - 9 Pounds
Length - 36" (adj stock at its shortest point)
Barrel - 16" or longer
Also has specs for a suppressor.
Depending on who you talk to, there could be a lot of competitors (KAC SR-25 EC M110 K1, H&K 417 or MR762A1-SD, FN SCAR or MK 20 SSR).
Given how typical Govt procurement goes, I wouldn't even try to make a SWAG as to who it will be.
There is still a need to produce a product that will pass the tests, and small arms are very scrutinized by a lot of different people. If it was that way, the M14 would have been the standard service rifle until its abysmal performance spurred someone else to grease the wheels of the system, despite Army Ordnance's attempts to sabotage the AR15.
I'm using a Hogue pistol grip and a STR stock on mine. The Mk6 is a decent 3-15x, the combo doesn't weigh a ton. Shoots < 1' at 100. Soft shooting, practical accuracy is fine for what it is. I'm prob. loosing 100+/- fps when compared to a 20" barrel, the 16' is relatively compact. Eats anything, loves 168s.
As a civilian user, the 16" semi makes a lot of sense to me. 20" guns are heavy and really too long to run and gun at all. If it's going to be a stationary position (prone, bench, etc) than why bother with a semi at all? A bolt is easier to shoot and more accurate. If the idea is to be more versatile than a bolt gun, the 16" semi accomplishes that much more effectively, in my opinion.
7.62 NATO bolt guns were ditched long ago after the failure of the M24 and UK AI's to be viable fighting rifles. M110 & LMT MWS are the answers to that.
Big Army is finally coming around to the reality that long guns don't provide any real external or terminal ballistic advantage, especially when you feed a 16" 175 SMK's.
Problem with guns meant for prone/bench, is that they really suck when you have to shoot positions, and someone seems to have forgotten to coordinate with the earth to drop in a flat range wherever there's a firefight.