The weapon skill does indeed affect that, the wiki I guess gives the highest available number. Also, your weapon isn′t worn out is it? That also lowers the number, naturally.
Not a bug. The wiki damage is about what you should expect if the weapon is at 100% repair, your supporting attribute (strength for melee weapons) is 100 and you skill in that type of weapon is 100. You can actually max your skill / attribute and repair the weapon to 125% and exceed the wiki figure slightly. That wiki figure is best used for comparison.