mtsurette,
I bought a new Ruger KMKIII678H a few months ago (MKIII 6 7/8” Stainless Hunter with fluted barrel). First thing out of the box I stripped and cleaned the gun. It took about 25 minutes or so because I was not following the instructions correctly.
I then took it out to the range for an initial break in session ~ 200-300 rounds of mixed .22 ammunition. No problems what so ever. No FTE’s, FTF’s, and both magazines worked fine.
I then put a Bushnell 2X6 scope on it with quick detachable rings. Then bought a holster and back to the range I went for round two to zero in the scope. After an additional 300 or so rounds down range, no problems what so ever.
My intentions are for small game hunting and punching paper.
There are a few changes to the MKIII versus the MKII (Loaded Cylinder Indicator, magazine release moved, gun will not fire with magazine removed). There are after market bushings, triggers, etc. to investigate if you want to modify your pistol.
I am very happy with my MKIII purchase – have no buyer’s remorse what so ever.
Good luck with yours.