MK I, II, III questions

Help Support Ruger Forum:

B.L. Hall

Dec 15, 2006
Madison, OH, USA
I have a MK I, I need a magazine, are the II and III the same or different?

next, I have seen MK II and III uppers for sale, would they fit on my MK I? I would like a bull barrel.

sorry for the stupid questions I just don't know anything about these guns. I picked this one up in a trade; the guy had to make up the difference. I was looking to sell it, but maybe I'll keep it.


Ruger Guru
Sep 18, 2002
Lake Lure NC USA
Ok,, while the answers may seem easy,, it can be a little confusing.
MKI mags of the earlier vintage will not work in later MKI's or MKII's. They are easily identified by the single slot for the follower button.
The later MKI's & MKII's will have a slot on both sides to allow that magazine to be used in the MKI's of older vintage & still be used in the MKII's. You just might have to swap sides of the follower button. The MKIII is a whole different animal due to the new mag release position & slot.
To confuse things a bit more,, the MKII 22/45 & the MKIII 22/45 mags will interchange.
As for swapping around uppers,, the short answer; usually they will swap. However,, there might be a fitting issue that's easily worked with in the gripframe tab area where the reciever locks in. If I were gonna get a different upper, I'd look for the MKII ones.
I hope this helps!