crossbows

[gayare'dion]

i have 2 questions, about crossbows, one not really doing anything with lord of the rings.
are crossbows ever used in warfare in middle earth ?
and how long does it take to load a crossbow ? i was watching mail call on the history channel, and they were firring one, and i always wondered how long it took to load one, but right when they were starting too, they would skip right to firing it.