Sounds more like you have bad collision on it, just switching the static mesh on the weapon shouldn’t have any different effects. Literally clicking on the static mesh in the actor and changing the mesh it references should work fine. When you convert from skeletal to static it likely doesn’t have any collision then, you need to generate some for your model.
As for a standard GrippableSkeletal, no it wouldn’t behave like that, the gun is customized with the settings it uses to behave how it does, you would have to copy the gameplay tags and setup it uses into any new grippable you want to copy it. The GameplayTags in the template for grippables define what buttons grip and release it and how, in a normal game these wouldn’t exist but they are there in the template for maximum flexibility and to allow me to demo all of the different features.
Edit Oh, you will also need some Sockets on the new mesh if you intend to use the exact same gripping logic (snap to handle, ect), look in the mesh for the template gun and copy over the named sockets in there to where you would like them on the new gun. For advanced users you can switch to components and the like as well but generally the socket method is the most flexible.