The steel frame Ruger .22 pistols such as the MK1 and MK2 were designed with ease of manufacture in mind. Complex machined components were avoided where possible and replaced with high quality stampings.
Accurate, reliable and inexpensive, Rugers seldom require the attention of a gunsmith except for custom work. One minor issue I run across when tuning Rugers is loose ejectors. The ejector is simply stamped sheet metal formed in a "U" shape and riveted to the frame. The rivet is soft steel and may work loose after thousands of brass cases have impacted against it.
Even when loose, the ejector can't go anywhere, since it is captured by the grooves in the bottom of the bolt but it could cause erratic ejection and should be fixed. I'd like to see the riveting fixture Ruger uses but I'm sure it's too elaborate for the home shop and to my knowledge no one makes one for gunsmiths so we had to design our own.
Basically, we just need a wedge that will slip under the head of the rivet in the receiver to act as an anvil while we peen over the other end. I used an old 8-inch flat file with the edges ground smooth and one side modified for a good tight fit under the rivet.
An old business card was inserted between the file and the receiver to avoid scarring. As the "anvil" was tapped into place under the rivet head, the peened-over end popped up slightly, revealing a gap between it and the receiver. All it took was some tapping from a small ball peen hammer and the rivet was re-set and the ejector tight.
A more sophisticated tool could be made from a spare bolt by welding up the bottom rail and re-cutting it at a slight taper on the milling machine so the bolt acts as a wedge and the ejector would stay aligned with both ears in the bolt grooves where they normally ride. But that's a project for another day.
This old Ruger MK1 is set up for NRA Conventional Pistol shooting with a Clark barrel, Ultra Dot sight and Marvel trigger. It is accurate and reliable.
Ejector and Rivet
Here's a Ruger factory ejector and rivet. Norcross says the ejector won't fall out even if the rivet does, but you will experience erratic ejection.
Bottom of the Receiver
Here's the peened-over end of the rivet on the bottom of the receiver. If you get the rivet properly flattened into the receiver, the ejector will be tight.
8-inch flat file
Norcross modified an 8-inch flat file for use as a wedge to support the rivet in place in the ejector. The edges are ground smooth to prevent scarring the pistol.
File and Receiver
The modified file is inserted through the back of the receiver, lining up the ground edge under the rivet head. A business card under the file protects the receiver.