Oh, are you referring to the door tooltips? Is your Commander marine Support class? I thought you were referring to floor tiles and space strikes when controlling the Commander.
There's currently no way to visually see how far marines can fire. I'm not saying this won't be implemented, but there are a few edge cases where this might not be desirable, like if firing range exceeds sight range - complicated because these two are measured differently. I'll think on this, though, thanks for bringing it up.
As a general sort of notion marine class weapons have ranges that approximate their relative real life counterparts, e.g. shotguns will have less range than long rifles.