Thats where I am a bit confused. If he is using his weapons then shouldn't I use the harm value of his weapons rather than 3-harm?
If the gunlugger'd use them as they should, yeah, they'd do damage as established. But when they're not to be fucked with, they're a one-man-army, shooting left and right and above and behind and keeping their own ass from a lot of people's line of fire. 3-harm is the best they can do in that situation, and it's already pretty rad as is.
Now the player has the choice not to use NTBFW, deal their full damage as established and count as a sole person instead of a small gang. They're not going full throttle but they retain a modicum composture.