| Kitrath |
Based on past threads, this question has come up several times previously, with varied answers as to if it can be done, or how it would work. Several people concluded that the Heavy crossbow could be fired by a medium creature at a -6 penalty but not reloaded ever except by a large or larger creature. Others concluded that it could be used two handed at only a -2 penalty and could be reloaded as normal. Some said that it could not be used by a medium creature at all.
Long story short, there was no verdict or consensus reached in the rules threads I could find. After searching I found a reference to a large heavy crossbow in Council of Thieves; this large heavy crossbow could be fired by medium creatures using two hands at a -2 penalty, and reloaded as a full round action. This seemed like a definite rules answer but there was a catch, in Council of Thieves, in the AP, the large heavy crossbow was mounted to the top of a carriage.
Since being mounted has no bearing on how a Large heavy crossbow is reloaded, the AP was able to confirm at least that a medium sized character can reload a Large Heavy Crossbow (and by extension a large light crossbow), the question is simplified;
Can a medium sized creature fire a large heavy crossbow, and if so, what penalties do they experience for doing so?
TL;DR, Council of Thieves AP lets medium characters fire and reload a mounted large heavy crossbow two handed with only a -2 penalty, so can a medium character carry around and use a large sized light or heavy crossbow?