Hello!
S'mon said:
Typical modern hunting bows average around 40lb draw weight, that's something like a D&D non-mighty shortbow (edit: or D&D hand crossbow). AFAIK 100lb would be somewhat above average for a 15th century English longbow (the ones that caused spinal deformities in the archers), something like a D&D mighty longbow +2 damage (edit: or D&D 'heavy' crossbow). A 140lb draw weight bow would be at the extreme limit of possibility, like some found on the Mary Rose, something like a D&D mighty longbow +4 damage.
Perhaps if we match draw weight to Light Load (on the Carrying Capacity Table) we can determine X-bow strength bonus.
eg. 120lb draw weight X-Bow = Str 20 (+5 damage)
300lb draw weight X-Bow = Str 26 (+8 damage)
500lb draw weight X-Bow = Str 30 (+10 damage)
You could maybe set it up:
Light +5 (Str 20); Medium +7 (Str 25); Heavy +10 (Str 30)?
The strength bonuses would also be effective vs. AC.
Making a X-bow in the hands of even a novice pretty deadly.
Maybe adding +5 Strength (effectively doubling the load) each time as you go up to seige weaponry. In addition to the base damage increase of x1.5 for each larger size category of bolt.
Repeating X-Bows would be at -5 strength (or perhaps as much as -10)?
Light X-Bow 1d6+5 (and +5 to hit)
Medium X-Bow 1d8+7 (+7 to hit)
Heavy X-Bow 2d6+10 (+10 to hit)
Light Arbalest 3d6+12 (+12 to hit)
Heavy Arbalest 4d6+15 (+15 to hit)
Heavy Repeating X-Bow 1d8+7 (+7 to hit)
What do you guys think?