How can I make models, such as weapons, part of an animation?

You could animate the actual object which would require making it a valid model that can be animated then do what I say next for it to be even better.

However if you just weld the object to a Dummy and animate the dummy with that tool welded AND unanchored, you'll be able to properly animate the character to move their arms to a certain location on that tool.

While a tool or part is welded to a dummy and you start creating an animation with the dummy, that tool will move with the limb you are editing on the plugin. So, doing this with say a gun welded onto the Right arm, you could easily position everything how you want then create the reload animation and just play it.

Here is a link to see how you should set an object up for animations (If you want to be fancy with that tool or object)... --> Link <--

You could also look up CFrames and perhaps lerp parts of the object instead of animating it.

Comment any questions or concerns bellow