I personally hate bolts and crossbows, they're way too slow, and the action of firing looks rather stupid. I wouldn't pick up the bolts, just fire away and let them fall, unless you train at minotaurs, when you get an iron arrow drop, you might as well pick them up. But, this could also work any where you get a nice drop. Xp, with hitting all ones, would be a lot, 600,000 xp, this is with the bronze arrows, without picking up. Since you wont hit all ones, you'll miss a lot, and hit a lot more than just 1s, the average xp would be around 600k. Expect around 1m+ xp from the bronze arrows, with picking up.