Dean finds Richies body by tracking his phones GPS to the demons hideout which would require a signal. However, later, when Dean is trapped in the hideout, his phone cannot find a signal to contact Sam. this can be explained by them having different carriers, though, especially in the 2000s.
When Bobby is test firing "The Colt" at a target, it is seen hitting too low and he is adjusting the sights. The notch on the hammer in the cocked position is the rear sight on such a weapon. Bobby's adjustment is filing the notch deeper. Lowering the rear sight causes a gun to fire even lower. A weapons expert like Bobby would know this.