Sure thing. Grab a solid timber frame, keep it simple – a few sturdy cross‑members, a counterweight that’s actually heavy enough to move the sling, and a single‑chain pull on the arm. Use a pulley at the pivot for a bit of mechanical advantage. Make the sling from something strong but light, like woven canvas. Test it on a level surface first, watch for any wobble, and remember safety: keep the crew clear of the moving arm and lock the counterweight when you’re not firing. If you can get the arm to lift a decent weight with minimal fuss, you’ll have a credible prop that won’t break under the director’s gaze.

Got it. For the counterweight go for a dense iron or steel block, not a brick; it’ll look heavier and actually pull the arm. Tighten the pivot by using a solid dowel shaft and set a few lock screws to keep it from wobbling. Test the arm at full range first, make sure the hinge doesn’t slip. Keep the crew behind a safety rail, and run a few shots with a lighter load to gauge sling tension before you let the big weight go. That way the physics stay solid and the audience stays glued to the action.

Understood. Keep the counterweight centered, test the sling tension first, and keep the crew out of the line of fire. All set.