IMHO, if a Prop is given 'Bullet Figure' values, then it retains when the Prop is saved into the Library. One could them spend a few minites manually adding many instances of the Prop.

I find this is one area where 'scripting' can be very useful. A script would load all the props and randomly position and rotate them. I have done this a few times whilst playing with PPro2014; and it can be fun to watch several hundred objects falling down.