Seems these weights are entered numerically as pounds, but are implemented ingame as kilograms. The M200 should weight about 22lbs, but weighs about 22kg ingame, the 12.7 lynx is 38kg ingame and should be about 38lbs.

With the new fatigue system, this is a problem as the weapons system weighs so much you are severely encumbered before you begin to add any ammunition.

Sources:
https://en.wikipedia.org/wiki/Gep%C3%A1rd_anti-materiel_rifle
http://www.sero.hu/advantages.htm

http://www.cheytac.com/408-375-m300-intervention/408-cheytac-2/408-m200-intervention/
https://en.wikipedia.org/wiki/CheyTac_Intervention