I built it, powered it but it can't fire. clicked on it shows red light, disabled and gives notification 'disabled by script' I don't see it in my mods folder and have no option to mess with it from the in-game mod menu.
Kinda sounds like a corrupted installation. Can you reinstall the mod?
“disabled by script” will normally come if the artillery has not enough power.
You should have a zip-File called “bigger-artillery_0.4.1.zip” in this folder: %appdata%\Factorio\Mods
