What exactly are you using to make the weapon model and the animations?
Don't know where he got the model, but judging from its detail it's probably downloaded from a model resource site.
The animation is just the shotgun animations sped up very fast, and honestly it's very messy from how its made. I've made some general improvements to it like putting it on the Pistol animations and giving it spread, but I have to come home to tinker some more with it.
Actually, here's a video of what progress I've done with it. Looks a ton better than it did initially.
