MKIV Ruger mags in MKII

Alexx1401 · Mar 11, 2020

Well add this to the I learn something new all the time

Was at the range today, had my MKII and MKIV among the mix. I accidentally put a loaded MKIV mag in the MKII. As I pulled the empty out I noticed it. So tried another. They lock in and feed perfect. So I do not know if it's just my old MKII or if this will work for all. Now that I know I will be ordering some more MKIV and get rid of the old MKIII mags I had kept to use in the MKII. Will be nice not to have to have 2 kinds of mags for the pistols now! This is how it looks with a MKIV mag in it. You can see the gap at the bottom but caused zero problems for the feeding, at least in mine.

SGW Gunsmith · Mar 12, 2020

You can also add the Ruger Mark III magazines for the 22/45 pistols to your list. They'll work as well.

Alexx1401 · Mar 12, 2020

SGW Gunsmith said:
You can also add the Ruger Mark III magazines for the 22/45 pistols to your list. They'll work as well.

I have several from when I had a MKIII, they do not fit the 4. I got rid of the MKIII as it was the only pistol of Rugers I have ever owned that pissed me off no end. After I stock up and some more MKIV mags I will sell off the rest of the MKII and MKIII mags since I will no longer need them. The difference is the II & III is the III have a cut in them to activate the mag safety on the MKIII but the base on them does not allow them to fit the MKIV. They have new bottoms that are supposed to make the II and III mags fit my IV but last time I saw some they cost so much it was not worth doing. Will just sell off the old ones and keep just MkIV since those will fit both the II and IV I have now.

SGW Gunsmith · Mar 13, 2020

So then, your Mark III was NOT a 22/45 version?

Alexx1401 · Mar 13, 2020

SGW Gunsmith said:
So then, your Mark III was NOT a 22/45 version?

Yes all of my MK's have been 22/45. The MKII and MKIII the only difference is the cut for the mag safety. The MKIV they changed the base. They are now flush with the back of the mag. When put in the MKII theMKIV, leave a slight gap but at least on my MKII they feed fine. Here is a pic of 3 mags. The one on the left is a MKII, one in the middle is a MKIII, notice the cut up high on the mag. That is for the mag safety. The MKII did not have that stupid safety so they did not need the cut. I have left over from when I had a MKIII several more MKIII mags I kept as they fit the MKII. The one on the right is a MKIV. You can see the way the base is flush with the back on it. I have "heard" you can grind or shave down the base on the MKIII base to make them fit the MKIV pistols. More work than I feel like doing since I can just sell them and buy more MKIV mags now that I know the MKIV mags will work. I will get rid of the MKII and MKIII mags I have then when I take the pistols to the range all the mags will be MKIV and will fit both pistols. Last I looked they were selling new base plates for the MKIII to make them fit the MKIV but they were expensive enough I did not want to bother going this route since they are easy to sell as is.

SGW Gunsmith · Mar 13, 2020

The cut for the magazine safety? Are you referring to the notch on the top left side of the magazine? If so, that's for the tail, or fin on the back face of the trigger. When the trigger is pulled that fin engages that notch and makes sure the magazine is seated properly to feed rounds. So, I suppose you could actually say that the notch is DUE to the magazine disconnect sometimes not allowing the magazines to seat properly, but the notch is really for the fin on the back face of the trigger to engage.

Alexx1401 · Mar 13, 2020

SGW Gunsmith said:
The cut for the magazine safety? Are you referring to the notch on the top left side of the magazine? If so, that's for the tail, or fin on the back face of the trigger. When the trigger is pulled that fin engages that notch and makes sure the magazine is seated properly to feed rounds. So, I suppose you could actually say that the notch is DUE to the magazine disconnect sometimes not allowing the magazines to seat properly, but the notch is really for the fin on the back face of the trigger to engage.

Interesting, had read somewhere the notch was to activate the mag safety and that was why the MKII mags would not work in the MKIII. When I still had the MKIII I guess I should have tried the MKII mags in it then. I was told they would not work so never did try them. When I got the MKIII they were new and hard to get. Mags took a good while to start to show up unless you wanted to pay scalper price. I had a bunch of MKII mags, wish I had known they would work, I would not have had to hunt all over to buy MKIII mags. The MKIII even though I loved the pistol was a constant problem and PITA. Finally someone wanted the receiver for a project and I was glad to let it go as the MKIV is a dream to clean. Even the MKII is fairly easy. The MKIII was the only gun I have ever owned that I had to have the instructions open to get the damn thing back together.

In any case it will be great to just have a couple dozen mags that fit both pistols now. When I first got the MKIV I headed out to the range one day with it. Grabbed about a dozen mags and when I got to the range realized I had grabbed from the MKII, MKIII box. So the mag in the pistol was all I had with me :s0054:

SGW Gunsmith · Mar 13, 2020

Some owners will remove that fin on the trigger and then that will allow the use of the Mark III 22/45 & the first version 22/45 made during the Mark II era.

Alexx1401 · Mar 13, 2020

SGW Gunsmith said:
Some owners will remove that fin on the trigger and then that will allow the use of the Mark III 22/45 & the first version 22/45 made during the Mark II era.

When I still had the III I almost ordered a bushing to deactivate the damn mag safety a couple times as that was in large part why it was such a PITA. Had not heard of the other tweak you mentioned. I turned it into a paper weight one day (the MKIII) when I tried to put it back together. Thought I would have to send it to Ruger. So when the MKIV came out I bought one. Then when I called Ruger to see about getting an RMA if they would, some gal there walked me through how to undo what I had done over the phone. Said she does it several times a week. So for a while I had all 3. The damn MKIII did it again, I got it cleared again and that was it for me. I just wanted rid of it. Whoever came up with that design for the MKIV deserves to have gotten rich off it so I hope they did. Now Wife is probably going to buy that new one with a 10inch tube which is of course the other style. So will need more damn mags. I am going to end up with enough invested in mags to buy a couple more guns by the time this is over.