I've seen some outtakes, from Hellboy I think it was, and the director had to keep telling people to stop saying "Bang" when they pretend to shoot the gun.
I fully support the use of CG, it was my first career choice after all, but if you're going to do CG put some supporting effort into it. Really, a piece of wood, an elastic, and a weight(Essentially a slingshot with the projectile connected) would make a decent prop that at least pretends to have some recoil, giving you a basis around which to build your CG model.
So many movies now have multimillion dollar CG budgets, with no supporting effort. Sometimes the right people can pull it off, sometimes it fails horribly.