Ruger Mark IV modifications

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Feb 27, 2011
So far, I have made the following modifications to my recently-acquired Ruger Mark IV Target, to address what I believe to be its shortcomings. Make no mistake -- this is a great pistol, and a vast improvement over the Mark III.

1. Replaced the "holster-ripper" front sight with a sight from the Ruger Single Six, with the base ground to conform to the Mark IV barrel contour.
2. Removed the magazine disconnector. This is actually an assembly consisting of the hammer, the magazine disconnector itself (which wraps around the hammer), its spring, and the hammer bushing. (The bushing appears to be installed in such a way that it's not easily removable, and it holds the other parts together.) Replaced these parts with a Mark II hammer and bushing. (If you can't find a Mark II hammer, you can do the same thing with a Mark III hammer and Tandemkross bushing.)
3. Replaced the stock sear with a Volquartsen Mark II target sear. This goes a long way toward improving the trigger pull.
4. Replaced the stock trigger with a Clark Custom steel trigger. This required a little fitting. First, the trigger pin hole in the Clark trigger needed just a tiny bit of reaming so that the stock trigger pin would fit. More importantly, I had to do some filing on the frame, at the front of the trigger opening. This is because the Mark IV frame is a one-piece CNC-milled aluminum forging, as compared to the welded-together components of the previous Marks. This difference means that the front inside corners of the trigger opening are rounded, rather than squared. They must be squared off so that the Clark trigger can fit and function correctly. This is a very worthwhile improvement since the stock trigger is very sloppy. In addition, the stock trigger has a nub that engages the magazine. This is totally unnecessary and adversely affects the trigger pull. (The three things that vastly improve the trigger pull are replacement of the trigger, replacement of the sear, and removal of the magazine disconnector.)
5. Removed the little magazine ejector at the base of the grip. This is totally unnecessary once you remove the magazine disconnector.
6. Replaced the magazine release with one from the Mark III. The only difference is that the Mark III release protrudes less. I found that the Mark IV part made it too easy to release the magazine unintentionally.
7. Replaced the stock plastic grips with the laminated wood grips from the Hunter version. This is a vast aesthetic improvement. (Note that the orientation of the medallions on the Mark IV grips is different from that of the previous Marks.They are now perpendicular to the barrel rather than following the slant of the grip.)
AlexanderA, how good or bad is the Mark IV without all these changes? Would a person be better off buying a Mark I, or II, or III? But at any rate, thanks for your interesting post. I had no idea that the frame of the Mark IV was an aluminum forging.
The blued Target version has an aluminum frame. The stainless-steel Target version, and the Hunter version, have steel frames. However, all of these are CNC-machined from forgings, rather than being made of welded-together stampings as in the previous Marks.

Now, as to how good the gun is out of the box, I have to say the weak point is the trigger pull. (This is very important for a target pistol.) I have all the Marks, that I bought new in each case, going back to 1970. The only one that had a decent (unmodified) trigger pull was the Mark I. Starting with the Mark II, Ruger made the trigger pull heavy and rough, possibly for legal liability reasons. In the Mark II, I replaced the trigger and sear, and that took care of the problem.

The introduction of the magazine disconnector in the Mark III made things much worse, from a trigger pull standpoint. Clearly, that had to go, as well as the problematic loaded-chamber indicator. The Mark III also introduced the nub on the trigger, that was intended to make sure the magazine was fully seated, as the trigger was pulled. That's just crazy, in a target pistol.

With the Mark IV, Ruger got rid of the loaded-chamber indicator, but doubled down on the magazine disconnector. They even added some features, such as the extended magazine release and the little spring-loaded magazine ejector, to overcome stuck magazines due to the magazine disconnector. First reports indicate that the trigger pull may be "improved" in comparison to the Mark III, but is still in the 5-6 lb. range. I can believe that. I didn't measure the out-of-the-box trigger pull myself, but I had difficulty keeping the pistol on target while pulling the trigger. The modifications bring it down to the 2 lb. range.

Regarding which Mark to get, the obvious answer is the Mark IV. The new takedown system makes the previous Marks obsolete. Just figure on making a few modifications, if you want it for serious target use.
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