The MKII was the best of the series. I have to relearn how to assemble the thing each time, getting the mainspring assembly and hammer strut together is tricky. The more I do it, the faster I get. Last night, after a Bullseye Match, I did the reassembly very quickly. I had my hook pick in case the stupid hammer strut got under the frame cross pin.
The MKIII is even worse as you have to stick the magazine in and out to get the hammer to fall. In every point of departure from the MKII, the MKIII is a more complicated, confusing, and unreliable variation. The first MKIII's, the loaded chamber indicator rested directly on the cartridge rim. If you dropped the pistol on the loaded chamber indicator the cartridge would ignite. It also caused stove pipe jams in a Friends MKIII. We had the device milled, defeating the loaded chamber indicator function, but after that he could go through a magazine without a stove pipe jam.
My Ruger MKII Stainless is a reliable and accurate pistol
However, the factory firing pin was soft, peened/mushroomed in the back, and that caused misfires. I think the material is stainless steel which is shallow hardening. I don't need corrosion resistance in this application, I need toughness.
So I replaced this factory firing pin with a Volquartsen, which is made from an alloy steel. It works great.