Only problem with those splinter bolts is when you're dealing with monks or rogues with evasion. Dc 15 reflex save is nothing for them and then they take no damage. Even so, they can be useful against other monsters.
Taking the idea of the Steel crossbow, I got a knife bayonet on my crossbow instead, so that it now functions like a short spear I can shoot through. And of course put a wand slot into that as well.
To really get my things running, I'm also doing the crossbow in Bronze Wood, so that its a tough crossbow. Cause if it breaks, all the wands in it break too. Totally don't want that to happen.