Ruger Mark IV Magazine Tuning

Thought I’d share my procedure for adjusting magazines, or “tuning” for reliability. The below are a pair of Ruger Mark III 22/45 magazines that were modified to work in a Mark IV which was purchased without factory mags.

Starting at a safe location such as the range, insert a loaded magazine and hand cycle your rounds through the mag onto a surface that won’t damage them. These will be your baseline for comparison later, but note any additional issues such as feed issues.


Our first clue that something is amiss sits atop the bench in the form of tiny lead shavings. Feed may be affected and accuracy certainly not helped by damaged bullets.


Note the damage to the driving band (silver shiny spot) on every bullet cycled from the unadjusted magazines.



Each of those spots sits 90 degrees from the extractor’s witness mark, indicating contact with the front of the magazine as was confirmed by gently pushing rounds forward in the mag.


Let’s start with the basic disassembly, to assume nothing about the reader’s knowledge base. You will want a simple punch to depress the spring follower through the hole of the base plate or extended pad in our example.


Next begin carefully sliding the base off.


I say carefully because even though you are wearing your eye protection things have been launched by yours truly into the ether. A ready thumb catches the rod and spring.


and allows it to extend without damage or a scavenger hunt.


The follower and button are then slid to the bottom cut out of the magazine body (you’ll need to flip the magazine over to see where this is and align the button to push it out).


Once the button falls out, the follower, well, it follows.



Part II upcoming; tuning the magazine.

Simple enough so far, and a good time to inspect components, replace springs if you remembered to order them, and clean out any gunk.


I start with the feed lips and knocking off any sharp edges with a small sanding wedge using 400-600 grit, depending on what I find. Internal edges are the critical ones.


Remember both fore and aft to prevent any drag issues against the ammo as it cycles.



Next is addressing the known issue with our magazines, the front of the magazine body. Using a small round file, I carefully and evenly cut a bevel without deepening the cut out more than perhaps 1/32”. Finish with 600 grit wrapped around your punch to prevent any notches from being formed (not likely using 600 but humor me).


I did not include a picture of the magazine body’s follower cut out but you should run some 600 grit the length of it on both sides along with the internal spring path using a proper dowel diameter and the same 600 grit.

The loading button rides in the above track and can be lightly sanded for ensured smooth operation. See silver portion (post sanding, originally blued).


Just fold that paper till it fits snugly and run this around the entire circumference.


Having addressed the metal, we continue to the follower and removing any mold lines present, paying the most attention to the sides which contact metal.





After cleaning any residual shavings/dust and re-assembly you should have a correctly optimized magazine free of issues. Not all of the above will necessarily apply to your circumstances so adjust to your needs.

ms6852 said:

You taught an old dog today. I had no idea that the 22/45 magazines and the MKIV were not interchangeable. Of all the rimfire guns I own rugers are not one of them. Thank you for posting.

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Not only not compatible but the Mark IV 22/45 adds material which makes it incompatible with the Mark III 22/45 magazines. As I ordered a piecemeal pistol using separate upper and lower, I had to scramble for magazines last minute with shortages readily apparent at all of the usual suspects.

These are Tactical Solutions Mark III 22/45 magazines with the extended base pads modified (ok just chopped with my pocketknife and sanded) to fit. They were both available and less expensive than other options for OEM mags, but I learned a lesson on compatibility as well.

And now I will stand corrected; just read that the Mark IV magazines (and presumably earlier gens) are the same body for both Standard and 22/45 models while using different base plates.