Ruger MKII Blast Shield
To solve the problem on my MKII pistols, I decided to fabricate and install blast shields for the triggers. I went to the local hardware store and purchased some brass shim material that was approximately the same thickness as a soda can. In the past, MKII shooters have actually used the aluminum from soda cans, but I wanted to start out with flat straight metal. I also wanted to use a slightly different design than what others have used.
Instead of making a loop that fits around the grip frame lug, I made a tongue that would fit in the receiver recess on top of the lug. This had the advantage of helping to tighten up the pistol. The light gauge brass shim material is easily cut with sharp scissors. No tin snips are necessary. The tongue extending down into the magwell should have a curvature to it. Burnishing the underside of the curve will help the brass shield retain the curvature. I used hemostats as a bending brake to make nice well defined bends, including the compound bend necessary to fit the piece into the receiver recess. Make certain the disconnect and bolt hold back lever do not bind with the blast shield. Only a small amount of clearance is necessary.
Once I had the first blast shield fabricated, I used it as a template to fabricate blast shields for each of my Ruger MKII pistols. Before the pistol is reassembled with the blast shield in place, the trigger and action should be cleaned. If the grime is really caked on, only a detail strip and individual parts cleaning will do. If the pistol is not too dirty, a spray with Gun Scrubber and a bit of toothbrushing should do the trick. Once the parts are clean, lubricate them and install the receiver assembly back on the grip frame with the blast shield in between. Insert an empty magazine to check function, and then a full magazine for a live fire test.
The same technique can be used on the Ruger 22/45, and the MKI and MKIII pistols. The brass blast shield makes a protective shield that effectively keeps the dirt and grime off the trigger. Hopefully it will be years before my Ruger MKIIs develop that gritty feeling again.