Here's some more info. A crossbow generally has a shorter draw length than a hand held bow. For example, a short limb crossbow with a 14" draw shooting 5ggp is the same as a long limb hand-held bow shooting 10gg with a 28" draw. If all else is equal (same efficiency, etc.), the example crossbow with the shorter draw will shoot the 5ggp arrow at the same speed as the hand held bow will shoot the 10ggp arrow.
-Alan