Phrase for Comics: English to Latin

Arcuballistarius is the person who shoots the weapon.
The weapon is arcuballista.
Either way, it should be accusative.
So either Arcuballistarium if the person or Arcuballistam if the weapon.

Bestia means beast but I don't see that in the English version.
Is the speaker addressing someone as beast?

Manuballistula would be a small hand-held crossbow.
I assume the author is adapting the word to refer to a pistol.

Labaris conveys the idea of wavering or tottering rather than missing.
(Of course, if his hand wavers, he will miss.)

George, thank you very much! The author has meant a person with an arbalest thus it will be arcuballistarium. My apologies for not putting beast in the English text. Yes, the speaker addresses someone as beast. One question is left: In modern Latin, what will be a good solution for the revolver instead of manuballistula? I have heard suggestions: revolvulus and pistolium. Could I use one of them?

Misha~
I'm not very conversant with Neo-Latinisms or
Latin Neologisms. I guess either would do.
~George