Artillery range, 1st Century AD

[Sean Manning]

"Bolt throwing engines (edit: like crossbows) are simpler because (as far as I know) their bolts don't wobble like this"

I don't think I have ever seen a bolt in flight which didn't wobble. Admittedly we normally only shoot our machines at greatly reduced tension for public performances, but I have also observed the bolts wobbling when we have been testing at full tension, complete with all the disturbing and nerve-wracking straining and creaking sounds. I am not sure at what point the wobbling starts but I have always assumed that it begins at the point of release. It may be the shape of our bolts of course but when operated by an experienced crew they seem hit the target alright, so the wobbling doesn't seem to be much of an impediment to accuracy.
As to the aperture they could be shot through though, I would have thought that the general design of a scorpion would require an aperture at least as wide as the full head unit so as not to run the risk of obscuring the arms' arc of travel if the machine needed to be traversed (I am assuming here that the scorpion would need to be positioned close to the aperture rather than back from it).

Crispvs

That's interesting. I'm not a very good archer, and have never seen an ancient catapult or medieval crossbow fired except on video, so I'll take your word. I suspect that catapult bolts wobble differently than arrows do though.

It would be harder to move a large catapult to shoot from different angles than to move a crossbowman. This talk by Philon about dug-in engines outside a wall is fascinating! I would have thought they would be too vulnerable.