Training newbies, especially with semi-auto pistols, after two magazines, I often hear the cry that "My gun is no good, so and so told me to get it and it is no good, blah, blah, blah". I then take the newbies gun, load it and rapidly fire off a tight group. Carefully, making sure the gun is unloaded, I put on the safety (if any) and return the gun saying "Doesn't look like the gun. Maybe you are still shaking your wrist (in fear) and anticipating the recoil?" Take your time, practice slowly, following your set up steps and firing procedure and finish your box of ammo before you blame the gun. There is a certain amount of coordination required on your part even if you are not playing tennis. A few boxes later, they are usually ok. Sometimes it helps to let them fire a few through your gun (loaded by you!) to confirm that the results are not varying with the gun, but the person. If they want to go off and buy a compensator or trigger job that is their business.