How to animate weapon?

You need an idle animation, mainly for the Handle keyframe.

Also I made a module (and a script) that is useful for making tools compatible with animating handles, in a super simple way (almost as easy as a drag-drop placement)

Full details here:

Module: Motor6DHandler Module - Roblox

Do keep in mind the module is new, and never had any documentation. I recommend inserting, and taking a look yourself.

will definetely take a look on this! thanks in advance if this works.