Well put by Small Bore IMO.

In regard to purchasing a used G gun, not every G gun out there has been put through the ringer so to speak. Some are in excellent shape and are just as reliable if not more so than anything else on the used market. The key is to know what you are looking at in a used G gun and as Small Bore points out few of us do. Kirk Merrington is someone that comes to mind as someone who would know.