I can confirm that my assault rifle has inferior accuracy to a pistol or SMG, even at 12 tiles. Obviously, this makes no sense. I have 1 strength higher than the requirement (6). I haven't moved, as I'm out of combat just standing there. Reproduced once combat starts. Very bewildering.
I read each weapon very carefully for mods. There is no laser sight, scope, or any other mod that would affect this. I have noticed it with multiple weapons as well. It's not the lighting, since the lighting is the same if I remain stationary and simply swap weapons.
Edit: Now I'm realizing that the assault rifle can hit ranges that the SMG/pistol cannot. It's still surprising that the assault rifle reliably has inferior accuracy at the upper limit of SMG and pistol range.