breaking bad - How did they film the gun spinning scene?

I don't know for certain but given computer technology in the 2010s and the cost of computing power vs the crew cost of filming many times, it seems likely that the gun was rendered. The fact that a rectangle can be drawn around the gun spinning, completely separating it from the rest of the frame makes it even more likely that it was isolated and done by computer. If the CG element doesn't actually interact with the rest of the scene it's going to be easier and cheaper.

Now if--on the other hand--Walt were shooting the scene, he could easily hide a small electromagnet (perhaps removed from a toaster with an electric release?) that he triggers remotely from a button in his hand (modified garage door opener?) as the gun slows down. He'd need two for the two stopping positions, and he'd have to push the button at just the right moment.