A Nurse with a Gun

Sunday, October 12, 2008

The MKII Magazine Tweak

While shooting with QJ yesterday, our Ruger MKII pistol began to have occasional stovepipes with one magazine in particular. Stovepipes in a Ruger rimfire pistol occur when a particular pistol is just a little tighter in tolerances than usual. Click to enlargeThe problem arises with the location of the ejector and the fit of the magazine.

The top of a rimfire magazine has four "lips." The forward lips provide a feed ramp for the rear of the cartridge. The slanted vertical edge lifts the rim of the cartridge up and into alignment with the chamber. Do not mess with it.

The rear lips perform the function of restraining the next round and releasing it at the proper time. In new un-tweaked Ruger rimfire magazines, it can also cause delayed release of the feeding cartridge, and premature ejection of the spent shell casing. These two forces combine to bring about a stove pipe jam.

There is a tweak to be done on the Ruger MKII magazines, that will make every one of them reliable. After a bit of inspection, I realized that I had a "new" un-tweaked magazine in the mix. The rim of the spent casing was striking the left rear lip of this magazine and causing the stove pipes. I took the guilty magazine out of the rotation.

Tonight, while cleaning the pistol, I tweaked the mag. The forward corners of each rear magazine lip required rounding. The Tweak, Click to enlargeI used a Dremel, and was careful to keep the rounded corners equal on each side, and the inward curvature of the lip itself unchanged. I cut the final curve with a jeweler's file. When finished, I burnished them.

This performed two functions. The feeding cartridge would have it's rear portion released earlier, allowing for a straighter feed as the bullet approaches the chamber. More importantly, the corner of the left rear feed lip would no longer eject the casing. The spent casing had to remain in the extractor's grip until the ejector itself dislodged it. I removed the firing pin from the pistol, and checked the feed, extraction and ejection with live ammo. Perfect.

Often these stove pipe jams are blamed on the Ruger MKII pistol. It certainly appears the pistol is at fault when every magazine, even brand new ones from Ruger exhibit the same problem. By tweaking the magazines, they perform flawlessly in the pistol with closer tolerances, and they still work reliably in other Ruger MKIIs too. Why Ruger has not addressed this issue and made the rear lips rounded, I do not know. All I know is that the tweaking works.

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Blogger DouginSalcha said...


Thank you! Thank you! Thank you!

I've been plagued with 'stovepipe' jams for years with a number of pistols (but especially with my Mk II). I never knew what I could do about it.

Since you have solved that problem, I wonder if you might answer another question? If you can, good (if you can't that's OK).

I have a Marlin Mdl 25MN bolt-action in 22 WMR. It is a sweet shooting little rifle but I have one magazine that will not let me 'seat' a round; I'm wondering if the problem may not be something similar. Any Recommendations?

12:30 AM  
Blogger Don said...

Thank you, sir. You are both a scholar and a gentleman.

I, too, have long been afflicted.

7:36 AM  
Anonymous Anonymous said...

It works! thank you!

4:36 PM  
Anonymous Anonymous said...

I am also glad to learn this tip. Thanks!

8:26 PM  
Blogger Jerry The Geek said...

While being careful not to imply a lack of faith in your competence, Xavier, I note that the Dremel tool is commonly known as "The Gunsmith's Friend".
That is because, in the hands of the unhandy worker, it is often overused.

It is easy to remove too much material with a Dremel; it's much more difficult to restore metal which as been ground away.

A note of caution is in order here: Heed the advice, but be parsimonious in the amount of grinding you do. This goes beyond "Measure Twice, Cut Once" which is the mantra of the Carpenter.

Perhaps it would be prudent to encourage the would-be amateur gunsmith to take away less material than you think is needed, and finish the cut as if it was the final cut.

Then test it on the range. If it works, leave it alone.

If it doesn't work, take off a little more metal, refinish, and test it again.

When the job is done ... stop!

(Those readers who have an unlimited budget and unlimited spare time may ignore this unsolicited advice.)

11:18 PM  
Blogger Xavier said...

Right you are Jerry.

The photo of the before and after magazine can be enlarged by clicking on it to show how much I take off. Be careful not to overheat the lips, as the temper will be lost. I use a file to give the final curve, a burnisher to smooth out the file marks. The lips should be a mirror image of each other when finished to prevent misalignment of the feeding cartridge.

This is a case where more is not better. The right amount works great though.

12:24 AM  
Anonymous Anonymous said...

Isn't all that just a good reason to buy a Buckmark? ;)

8:21 AM  
Blogger Dink said...

Are the MKII mags the same as the MKIII? I have occasional problems with my MKIII.

11:17 AM  
Blogger Xavier said...

That I don't know dink. I suspect they are the same at the top of the mag, but don't take my word for it.

5:57 PM  
Anonymous Anonymous said...

I just got a Mark III Hunter and I'm having the "Ruger Stovepipe" problem with almost every 10 to 15 shots. I'm using Federal Premium ammo. While it sounds like your fix would solve my issue, I've called Ruger to see what their position is. After all, it is a brand spanking new gun with only about 200 rounds through it. The nice lady at Ruger said she'd never heard of the problem but would ask the engineers and call back. In the mean time, I sent her your article along with two other similar descriptions from other boards. (http://forums.gunboards.com/showthread.php?t=68428 Post #4 & http://www.thefiringline.com/forums/archive/index.php?t-307749.html) I'll let you know what they are willing to do. This clearly seems like a design flaw/manufacturing issue. Thanks for posting your article. I would not feel too confident calling Ruger w/o your info.

3:09 PM  
Anonymous Anonymous said...

Thanks from Brian & Larry Bandoli, from Davis IL.WE have had the problem for over six years with our mark II.(ever since it was new) Tried your fix today, and fired 700 rounds without a jamb. Did not file off as much as the picture showed-just slightly rounded the sharp edge. WORKS GREAT!

4:14 PM  
Anonymous Anonymous said...

Excellent! Worked perfectly!

9:49 PM  
Anonymous Anonymous said...

I just purchased a 22/45 Mark III and was having jams as well. Same problem with both magazines. Tried different ammo to no avail. I reworked one of the two magazines per the post and went out and put 200 rounds through it without a single jam. Thank you much. My other magazine is getting reworked in the morning. Must be a gun toting surgical nurse to come up with this one...

5:28 PM  
Anonymous Anonymous said...

I'm amazed at how effective this modification is. I had my doubts at first but I must say, this is an amazing little fix that costs nothing to do and makes a world of difference in the little Ruger. Thank you for posting this. It has made shooting my Ruger MKIII an absolute joy !

6:10 PM  
Anonymous Anonymous said...

Fantastic! Why doesn't Ruger do this already?

6:42 PM  
Anonymous Anonymous said...

I was very skeptical to try this mod, but at the same time excited to finally have an end to my stove pipe problem. I was used to at least to jams per 10 shots. After I modified the magazine I shot 300 rounds.. not a single jam. THANK YOU!

8:05 PM  
Anonymous Anonymous said...

I was frustrated by stovepipes on about 15% of shots with a brand new Mark III 22/45 Hunter. Figured if the fix was that easy Ruger would have modified the mads long ago. But I tried it and have had only 1 in the last 800 rounds!!

Ruger owes this fellow a commission and should offer to replace the mags.

Amazed but it DOES work!

Thank you for your work!

1:42 AM  
Anonymous Anonymous said...

Thank You for the tip! Brought a NIB Mark III 22/45 and was dumbfounded why it kept jamming every 3-4 rounds. Came home, read your tip, and now, 500+ rounds later not 1 jam! Thank you!

12:24 PM  
Blogger SharonAnne said...

Xavier, it is good to see another nurse in the shooting sports. I am disabled now but worked telemetry for 14 years. You have selected or perhaps it has selected you, the most noble of professions.
Excellent trouble shooting on the MK II magazine.

Be well

3:48 PM  
Anonymous Craig said...

Hey all, in response to the MkIII question about trouble feeding... i advised a friend, Ruger was one of the best. upon buying a brand new MkIII , she came to me with ammo feeding problems.long story short, after suspecting magazine problems,a couple of trips to different gunsmiths and several calls to Ruger,concerning returning the piece a representative finally told me that the new Ruger MkIII will "have the best chance of feeding reliably using ONLY " Remington high Velocity but NOT thunderbolt ( which no one should use due to wax coating build up)and NOT Golden Bullet.Will also feed reliably with Federal Lightning and Winchester Wildcat.. not all that easy to find these, but we have used the Federal Lightning and they solved the problem.Had much improved feeding and hope to find and use some of the others to test them as well.Pretty sad to pay that kind of money for a "Top of the Line " model and have to be so picky about the .22 ammo. I hope this helps some of you.From now on I'll be more careful as to what i recommend ..

10:20 AM  
Blogger bigdog632 said...

you say you burnished the ground ends how did you do that?

11:25 PM  
Blogger Xavier said...

Burnishing can be done by hand with a piece of metal that is harder than the piece worked. It's purpose is to remove the roughness left by tools. I used the rounded handle of a jeweler's file, which fit in the area nicely. A little pressure on three or four passes and the surface was smooth again.

6:30 AM  
Blogger bigdog632 said...

much obliged

11:38 AM  
Anonymous Anonymous said...

Thank you. After the mod, my MKII will digest anything.


6:21 AM  
Anonymous Anonymous said...

I had the exact experience. I bought a new 22/45, every couple shots stovepiped. I called the lady at Ruger who said it was the first time she'd heard of it and would have the engineers call me back...which they didn't.
Its a shame to see this company's quality erode like this. Thanks for taking the time to help people get their new Rugers working!

9:02 AM  
Blogger Unknown said...

Thanks man
Just bought some type of put together hybid parts gun.
MkI lower with a 22/45 top end
stove pipe after stove pipe
Then I saw some one had posted your blog on Ruger forum
I tried it this morning just before going to the range
WOW ......200 rounds no problems

8:42 PM  
Anonymous Anonymous said...

Add my kudos - new 22/45 Mk III had at least one stovepipe per magazine load, now no malfunctions of any kind. Thank you, sir!

4:56 PM  
Anonymous Anonymous said...

THANK YOU Xavier!!! Your website is exactly what 'surfing' should be, the reward of searching for useful information. Your article on "The MKII Magazine Tweak" has turned my $900 Volquartsen Masters into the joy to shoot that it should be. I would like to offer you my version of your 'recipe' to give to others on your site.
As a machinist, I quickly saw that your method could be achieved by (lightly) clamping a magazine in a mill vise (on a set of parallels)and milling off the offending 'tips'. I 'touched off' the ends of the tips with a 1/8 end mill, moved over .025" and slowly cut away the tips (I was at 4000 rpm). This gave me perfectly even tips, but as this area is curved, the cuts came out as a bevel of sorts.
Wanting to take this mod one step at a time, I DID NOT file the cuts flat, but simply smoothed all four lips on a very slow buffing wheel.
This magazine is now the ONLY one (of my six) that has zero problems, even with hollow points! The other mags will get the same treatment.
Thanks again for the info!

8:23 AM  
Blogger Richard said...


THANKS for the tip!!

I purchased a used MKII Competition Target last month. Nice gun, but it would get a jam every 15 shots or so, regardless of the brand of ammo -- very frustrating.

I tweaked both of my magazines per your suggestion, and have now shot over 100 rounds with ZERO issues.

Well done sir!

6:28 AM  
Blogger Grampa Steve said...

Thank you! I've done eight mags now, and all feed perfectly. Was getting consistent misfeeds where the brass was getting ejected into the action, some worse than others. This mod does the trick.

11:36 PM  
Anonymous Chris said...

Just finished this modification on 4 MK III mags and after nearly 500 rounds not a single stove pipe!!
Has anyone mentioned this to Ruger, I mean shown them this modification and the results thereof?? Thanks Xavier for your fix!!

7:47 AM  
Anonymous Anonymous said...

I've had a feeding problem with my MkII for years. Couldn't get more than 30 rounds off without a problem. Didn't matter what mag I used. Ten minutes work with a file and it feeds noticeably smoother when manually cycling it without the recoil spring. Took it to the range this afternoon and shot 200+ rounds without issue. Problem solved - THANK YOU - great mod!

6:14 PM  
Anonymous Anonymous said...

thank you .Ill relay this to my ruger crazed family .
~madcat4570 ~

9:34 PM  
Anonymous Anonymous said...


9:37 PM  
Blogger Jillian said...

I just acquired a Standard model made in 1971. It does not have the "A100" on the grip frame so takes the older 9 round magazine. I too have been getting these malfunctions though I believe my mag is beyond your mod since the sides have been pushed in till they split.
I will keep this in mind for my nest mags.

However, in researching mags I noticed some of these Mk.1 mags have a patch welded to the button side. Anybody have any idea what that's about?

Thanks for this info you posted.

11:23 AM  
Anonymous Anonymous said...

I am not sure that went through so I am trying again. My apologies if I have doubled up on you.
I just acquired a Standard model made in 1971. It does not have the "A100" on the grip frame so takes the older 9 round magazine. I too have been getting these malfunctions though I believe my mag is beyond your mod since the sides have been pushed in till they split.
I will keep this in mind for my nest mags.

However, in researching mags I noticed some of these Mk.1 mags have a patch welded to the button side. Anybody have any idea what that's about?

Thanks for this info you posted.

11:25 AM  
Anonymous Anonymous said...

Works like a charm! Great post.

6:59 AM  
Anonymous Anonymous said...

I bought the Ruger MKIII 22/45 and it stovepipes constantly. Sent it back to Ruger twice. Second time with pictures and a two page shot by shot synopsis. Ruger says they never have had a complaint with the MKIII 22/45. Got it back two days ago. Still stovepipes. I will try your magazine fix.
The Rock

2:29 PM  
Blogger george pace said...

Six years after your original post and still helping people... like me for instance. Shot a Steel Challenge match and rarely got off 5 shots without a failure to feed. Modified 3 Ruger mags and 3 Mec-Gar mags as per images above, and they worked nearly flawlessly. (I also removed the LCI and installed a Volquartzen Hard Edge Extractor after testing the modified mags and now they all run perfectly, so far.)
Thanks again!

10:19 PM  
Blogger Ken said...

Ive been having feeding problems with my Mark 3. After looking closely at it yesterday it seems like the front of the bullet is too low in the mag. I cleaned off the plastic piece that the bullets ride on and put a drop of Gorilla glue on it. I think this may fix the problem.

11:39 AM  

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