View Full Version : Ruger Mk III failing to lock back

February 26, 2009, 12:29 AM
This pistol was a gift, and I love it. It functioned flawlessly for the first 2-3K round count. All of a sudden it started failing to lock back at the last round. I hadn't cleaned it for at least 1K rounds so I assumed that was the problem. So, of course I cleaned and lubed it thoroughly , but it still does it. It does it with both mags.
The gun is basically still new in every meaningful respect, I'm getting ready to take it down again and see if I can find the cause, but may just try a different ammo first, still, it should work well with the Blaser I've been shooting and did for the first 500 rounds. Is there anything I should look at that someone has seen before? I'm wondering if the bolt isn't recoiling far enough to catch, (Ammo) or if there is still crud in whatever spring the bolt lockback uses to engage it. It always locks back when I cycle it by hand on an empty mag.

February 27, 2009, 04:19 PM
What I found, since no one answered. The hold back catch surface was hammered. I'm really surprised that no one else has had this problem.


February 27, 2009, 05:02 PM
It is a concern... I use this site for my ruger MKIII info...
every issue is addressed (yours too) and usually with excellent pics...

February 27, 2009, 05:10 PM
Thanks, uhhh, my photo skills need help, I know. :o

February 27, 2009, 07:30 PM
I wasn't ribbing you for your pic skills... rather anything you need to see there is a good image and may have arrows and description etc. right on the image!
I used that site to delete the mag safety and loaded chamber indicator from mine as well as how to do simple and deep stripping.

February 27, 2009, 08:58 PM
Thanks, I also removed the magazine safety some time ago, and saw in that forum where one can add take up slack adjustment screws for both ends of the trigger pull. I really do have a nice camera now but need a photographer to show me how to do really good closeups.

I took the bolt release stamping off and found that by grinding .020" from it's face on the original angle the worn area was full faced again. Reassembly proved it to work well again. Mention was also made in the forum that releasing the bolt using the thumb release is the probably cause of the dysfunction, and that sling shotting the bolt is the answer. I question that because mine looked like the surface was hammered rather than worn.

But in spite of that I'll be sling shotting it from now on.

Dr. Strangelove
February 27, 2009, 09:12 PM
I can't tell if you have replaced the grips, but my MKII fails to lock back if I tighten the top grip screw on the bolt lock side. I have replaced the factory grips with Pachmeyers. The rubber grips keep the bolt lock from functioning if screwed in too tight. I could modify them, but I find just not tightening the screw all the way works well with no mods needed.

You are correct, the bolt release isn't meant to be used to close the bolt by itself, like you would on a 1911.

February 27, 2009, 11:39 PM
Mine has cocobolo grips. I don't know if that means anything or not, but I dont tighten screws very tight. These are the huge wood grips with the thumb shelf on the right side.

Dr. Strangelove
February 28, 2009, 04:43 PM
In that case, I'd take a quick peek to ensure that the grip isn't binding the lever for the bolt release that runs under the grip. It should move up and down with minimal effort. It doesn't take much pressure at all to bind the lever so that it won't function. Given that the pistol functioned flawlessly for as long as it did, this probably isn't the answer, but it's worth a look.

March 1, 2009, 12:17 AM
No, the problem was a negative surface on the "bolt block assembly" where it contacts the bolt. Ruger calls it the bolt block assembly, to differentiate the part from another part from way back called a bolt block that is in the hammer strut area and is not relevant to the discussion. It's one solid stamping, so "assembly" is weird to me. Anyway, by grinding back to the original angle the problem went away.

Knowing about metals I may substitute (If I can) a blue part for the stainless one in the future. It's difficult to heat treat any stainless steels to equal the properties of carbon or alloy steels I'm thinking. Also, this part is inside the receiver so it won't be seen.

March 3, 2009, 03:04 PM
This is for the record, since people google for answers and here it is! I ordered a new bolt stop assembly (Not "bolt block" as stated earlier) as part # KA-37.
That's the blued model stop, as I'm hoping the carbon steel will hold up better to the battering it takes.
My fix on the original stainless part lasted about 5 boxes. Interestingly, conversing with the parts department at Ruger, the fellow said they don't carry the stainless part anymore (Part# KAN-37) to which I replied "Well, that's fine, you can't see it anyway". He also chuckled when I suggested the carbon steel part might hold up better, "That's been an argument around here for a while" he said.

I bought two of them for a total of $8 (plus shipping). That should last a while.

James K
March 3, 2009, 11:20 PM
It's moot at this point, but I have known people to forget that the Ruger bolt stop is there, and when the bolt stays back, they hammer on the rear of the bolt to get it to close. The result is the damage you have seen.


March 17, 2009, 01:16 PM
I'm embarrassed to report that the problem all along was my 1911 high hold technique. My right thumb rested along the left side of the receiver and was applying slight downward pressure to the release! Since making myself conscious of my hold the bolt locks back every time.

But that was too obvious to consider I guess.:o