I have a few guns like that that I just wont mess with. Royale and Boss... and my Daystate MCT's come to mind.
I love to tinker, but aside from some aesthetic enhancements to them, I just havent found a need to mess with them.
Hate to admit it, but that lack of tinkering keeps me from shooting them as much. Seems that when I get one dialed in 100%, I dont shoot it as much. But it's nice to know that I can go and get the Royale, the Boss, or either my MCT's and assuming I do my part, they will do theirs.
I've also had some guns that were good...but made better from people who know what they are doing. First to mind is a .30 Cricket conversion from Mr. Wall. I will simply not touch that gun in tinker mode. It's spot on in every way!