When catapult/ballista/cannon has been built, move it as you would move your soldiers. Then, whilst still having the weapon under your control, right click on the enemy fortification that you wish to destroy.
Beware, the enemy soldiers will attack your weapon if you get too close, too far away and the weapon will not fire.
It is true that when the start load is exhausted it is difficult if not sometimes impossible to collect a new load.
On the other hand, catapults, balistas and cannons are not of really good use, it is easier to take opponents towers with soldiers. The only good war machine is the amazon gong. Even then I almost never build one.
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by rakirkpatrick:
Thanks for that,
the main problem though seems to be loading and collecting the ammunition, even after I have produced 2 or 3 sets I don't seem to be able to collect it??
any help?? <HR></BLOCKQUOTE>
I think the easiest way is to go to your pile of ammo and click the collect ammo text in your menu. I was hoping that you could hold down the alt key and click the ammo pile, but that did not work. I was thinking the ALT key thingy should be the same as the geologist that will start searching for resources when you hold the ALT key in settlers 3.