depends on the map
for Vacant, Pipeline, Crossfire, and Wetwork i use the R700(i rather use the R700 because its as powerful as the 50. Cal but has more accuracy and is faster to reload).
for all the other maps i use assault rifles(M4, G36C, and AK-47) and i sometimes use sub-machine guns(P90 and AK-74u)
i use the same perks for all my classes(except the R700)... Bandolier, Stopping Power, and Martydom
i use Bandolier, Stopping Power, and Iron Lungs with my R700
