the only exeption is crossbows which need to be reloaded. rapid reload will give you another shot but thats it. you cant slot 2 bolts in a crossbow, you can however get a double crossbow if you want-
Double crossbow
Size: Medium; Type: Exotic ranged
Price: 200 gp (the repeating one is 300, if I remember well)
The double crossbow is, as the name suggests, a crossbow with two bows and two triggers, so that it can fire two bolts.
The user can either fire only one bolt or fire both bolts (making two attack rolls, but with a -2 to each; also the two bolts must target the same creature)
Even if you fire both bolts it is still a standard action and does not require a full attack.
Damage is like the normal light crossbow. Range is as light crossbow. ( heavy versions also exist)
Reloading a bolt is a move equivalent action (reloading both bolts is a full round action) and provokes AoO. The idea is that you can use it as a normal light crossbow if you haven't got time to fully reload but you want to keep on shooting.
The main use of the double crossbow is to fire to shots on the surprise round.
The difference between the double crossbow and the repeating crossbow is that with the rep. x-bow you can make multiple attacks but you need a full attack action, while with the double one you can fire to bolts at once, so it's a single attack (and so a standard action).
As a sneak attack only one shot counts.
Inspired by ladyhawke