I can think of a way to possibly make bullets richochet of the ground, by changing their velocity once their Z coordinate is near zero. However, it is very difficult to detect other surfaces besides the ground. I guess you could continuously record the position and velocity of a bullet, and then once it becomes null (i.e. hits something) you could camcreate another bullet at the last known location, and send it off with setvelocity. However, there is no way I can think of to find the angle of the surface the bullet hit, so there is no real way to know what direction to send the new bullet.
In short, I can't think of a way to make it work, and I think it would be a waste of CPU anyway, since you would have to keep track of every bullet flying around. And most of the time in OFP you are in an outdoor environment anyway, so it's not like you're going to be killed by a bullet ricocheting off the dirt or something.
And did you say you want bullets to Ricochet off of people?! :-X