Upgrade Crossbows and Crossbow Bolts
To upgrade your crossbow and it's bolts talk to Sorine Jurard of the Dawnguard. If you haven't already recruited her then do so. She will send you on quests for Dwemer schematics that will improve crossbows and bolts. New crossbows can ignore 50% of armor when attacking and one of the new types of bolts explodes on impact. Once you bring the schematics to her, she will teach you how to craft them yourself or you can buy them from her later when she has them.
Added by: AK GMAN14 Jul 14th 2012, ID#8531