I doubt that the snipers in the pictures are JTF. However, since snipers are still considered elite forces, and practicing unconventional warfare, they‘re still accorded anonymity as stealth is as important in their line of work.
As for the rifle they‘re using, it‘s a Stoner.
Effectively, a flat top M16 chambered in 7.62 by 51, semi auto only, with heavier barrel, reinforced butt, and a few other shiny bits (it was designed as a sniper rifle as opposed to other weapons which were modified for snipers). It looks like they‘ve added some form of kite sight or other optic device to the top, which is not uncommon. The whole thing weighs over 10 pounds, unloaded, with no optics.
And I also doubt it‘s that Diemaco rifle either because:
1. 5.56 is a VERY poor ammo for sniping
2. 600m just isn‘t enough range
Most armies use 7.62 or 50 cal. The Canadian sniper who beat the record was using 50 cal... I think in a Barrett