I carried both of those guns back in the late 80's into the early 90's when my agency made the transition away from revolvers. As noted by some of the other posters, the newer generation 4506 had a bit better track record than the 645. We had no serious service/reliability problems with either model, though the trigger geometry was a bit better on the 3rd Gen 4506. As a side note, we also had an inventory of the compact 4516's, and they were NOT as reliable as the full-size versions.
