1. Join NF 2. Go rifleman with HMG 3. Go prone and fire the HMG 4. Your stamina does not drain. Stamina drain happens with the BEHMG, so unless this is some weird asymmetrical balance, I'm pretty sure that one of the sides is bugged.
Just fixed it in SVN. For some reason, BE HMG had a drain of 1.0, whereas NF HMG had a drain of 0.2. Brought NF back in line with BE, so next patch will have this fixed. Good catch. Closed.