if anything, use crossbows to level your marksmanship skill... and just wait until you can get one of the best guns after, oh, lvl 49 or so :P
By that point you'll have the gun equivalent of sidewinder, and long since have barrage... those two together will equal positively sickening damage. Especially if you have the right bullets, which more often than not have a substantially larger damage potential (what, twice the dmg or something? not sure...)