Weapon customize system

Hello I was wondering if anyone could help me out with this.
How can I have a gun and add different attachments to it with still keeping
the same reload, walk, run animation. And would animation be used to look down the
sights? Or would that be done with a script?

Thank you so much for helping me even though I ask a lot of

This should be no problem with animations, as long as you’re not changing the object’s child structure. Add the modelled attachments as a child to the gun, and see if it works good enough to use. You can then enable or disable them through script.