Over the years I've read enough about the remedial need to "fit" aftermarket triggers to Ruger Mark pistol grip frames to cause me to ask, WHY? While I personally haven't encountered the need to do any actual adjustments to any of the aftermarket triggers, I have found that there's more of an inconsistency with how the cut-out in the grip frame was performed during manufacture at Ruger. Every time I've encountered any severe scraping on the sides of an aftermarket trigger, it's been caused by some very nasty roll-over burrs in the grip frame cut-out for the trigger. The assemblers at Ruger must be wearing "chain-mail" gloves during the installation of triggers, or they have a "first-aid" kit nearby with Mercurochrome and band-aids at the ready. Some of the horrendous, jagged edge, burrs that I've removed would probably have skin and DNA on the edges of one or more of the burrs from the assemblers at Ruger, if those edges were to be tested.
Here are some of the width dimensions I've measured on aftermarket triggers using calibrated digital inspection equipment:
Ruger Factory Trigger
Volquartsen Stainless Steel Trigger
Volquartsen Black Aluminum Trigger
Clark Custom Trigger
S.G.W. LLC Custom Trigger
Digital measuring equipment doesn't LIE. The "jaws" can be zeroed-out, when closed, before each, and every, measurement is taken. While the above triggers show only one of each variety, I have measured the width of every aftermarket trigger that I install, before I install it to verify that it falls within these dimensions. The basic dimensions as listed above, don't vary enough to warrant mention here, as they are in the ten-thousands of an inch range and will never affect the fit into the grip frame, once the grip frame cut-out checks to be of proper size.
So, before any attempts are made to install an aftermarket trigger begin, check the cut-out width in the Ruger Mark pistol grip frame to see if there are any burrs that may be causing the width of that cut-out to be smaller than 0.374-inch (3/8 ths). A gauge pin, gauge block or caliper will give you the current width. Drag a cotton swab (Q-Tip) along the edges of that cut-out to verify there are no cotton fibers being pulled from the swab. If fibers are being pulled off, it's a burr or sharp edge doing that, and that edge needs to be smoothed with a fine-cut file, Arkansas stone, or #400 emery paper backed by a small sanding block. Burrs dragging alongside of any trigger will give you a gritty feeling trigger pull, and who needs that?
Now, with the width of the cut-out in the grip frame verified, or worked over, so it does indeed measure 0.375-inch, and the triggers having widths as recorded above, there's no reason to expect any aftermarket trigger to NOT
fit in a steel grip frame Ruger pistol.