You could just remove it from the character or when the player drops it,set the velocity of each part in the direction you want it to be thrown, then parent it back.
Or you can move all the parts into a model, then use a body position to move it back and forth and make it a tool again
Your gonna run into issues with the model stuttering around in a live server because you will have to use a server script move it. I suggest making a clone of the object in the workspace and having it play an animation of the object flying forward.
As an added benefit you can put some satisfying spin onto the weapon