Those shims are available to you through sources like Brownells and people with little or no pistolsmithing knowledge or experience install them to "Tighten" something that isn't at fault to begin with. I'd suggest removing the offending shim and put the feeler gauges away, take it out and let fly. I think you'll find it will load, cycle, discharge and put a bullet downrange just fine. They aren't a Jerry Miculek special or even approaching it. They were to defend one's self. Put things back to original and enjoy.