After 500 rounds my new SR22 started to shoot eratically. I tried to sight it in and gave up. Got home to clean it and found the barrel extremely loose. The gun did not come that way; the barrel was tight. My problems is that I can't find an allen wrench that fits to tighten it. The manual says it's a 3/32" allen wrench. Nope, too small. a 1/8" is still too small. But a 5/32" is too big. What gives? I'm very surprised it loosened on it's own after 500 rounds. Has anyone else had the problem? Does anyone know the allen wrench size that will fit that screw under the trigger?