Ruger MK 1 chamber issue

[vinmarvin]

Bought the pistol couple of years ago out of an estate and till 3 weeks ago had no issues with it. Went to the range to shoot my postal scores for NHSA and was using the CCI copper head rounds at 1250 fps. Within the first 5 rounds I heard and felt something different to the usual sound and recoil. Picked up the brass and noticed a small hole blown out at the bottom of the empty case. The holes were directly opposite to where the firing pin was striking the round in other words blowing out directly on the feeding ramp at the bottom of the chamber.

Took the pistol to the guys in the gunshop on the same premises and we both agreed that the amoo maybe too hot although I've used the same ammo numerous times before. I then fired a couple of S&B standard rounds through it and even a couple of S&B sub-sonics at 950 fps. Although none of them blew a hole through the case they all had a small bulge at the exact same location.

The gunsmith at the range took a look and according to him someone worked on the feeding ramp and accidently damaged the bottom portion of the chamber. The chamber is now missing a small piece right were the round enters from the feeding ramp. According to him he cant work on that area of the gun and I now own a nice looking paperweight.

Anybody experience this before and is it worth getting a second opinion or should I make it a center piece in my display cabinet?

Thanks guys

[oafpatroll]

The diagnosis of the cause sounds off to me. You shot the gun over years and even with the same hot ammo without issue and the problem presented in the middle of a session.

Is the defect visible?

[Meteor]

I handed a SAPS officer my Walther PP 22 to feel it and he proceeded to dry fire it a few times leaving a lekker dent on my chamber face. Is yours the same?

I think the solution mentioned for mine was ironing?.

[A-R]

It may be possible that the feed ramp was polished (ground away) excessively, but that would have been an issue from the start.
If that is the case, just stick to ammo that feeds and fires without issues, like the Standard Velocity and Subsonic ammo that you used.
You are probably not going to reload the cases, so what they look like is irrelevant.
ALWAYS wear safety glasses when shooting!

However, these Ruger pistols have a tendency to build up dirt and bullet lube residue in the chamber. Especially the target versions (Mk1 is the target version of the Standard) may have tighter chambers, which are less accommodating of dirt. My Mk11 Target version certainly is very sensitive.
Nothing wrong with the pistols, it's just the 22LR ammo that is notoriously dirty.
When the dirt starts to accumulate in the chamber, the cartridges chamber with resistance. At some point, the cartridge does not fully chamber any more, resulting in a bit of the case sticking out of the chamber when you pull the trigger. This can result in a bulged or even ruptured case.

My advice is to scrub the chamber (and barrel) properly with solvent and a phosphor bronze bristle brush and inspect it closely for any residue. All the old hammered-in gunk may take some effort to get out. Once clean, test it again. This will most likely solve your problem.

The Ruger 22 pistol manual says it is safe to dry fire. Indeed, you have to dry fire it in order to disassemble it. I have dry fired mine many times and there are no marks or damage anywhere.

[krieger]

what A-R said "clean the barrel" It is probably leaded up; it will cause overpressure.

[MSW2]

I handed a SAPS officer my Walther PP 22 to feel it and he proceeded to dry fire it a few times leaving a lekker dent on my chamber face. Is yours the same?

I think the solution mentioned for mine was ironing?.

The way the Ruger is made that cannot happen. Unless the pin keeping the firing pin from going that far is damaged. But I doubt it.

[MSW2]

Pics? The top of the ramp can look a but suspect when it is not.
I would go with the A-R dirty chamber theory for a start.

[Heath Robinson]

Not sure what yours looks like, but there is a very small step between the chamber and the feed ramp to make room for the rim on mine. Not sure if this is what the gunsmith saw.
I agree that a polishing job or any other feed-ramp modification would not work well for years and then suddenly start blowing holes in case walls, and thus agree that fouling somewhere is probably the cause of the issue. Either in the chamber, or somewhere that prevents the bolt from closing completely.

Start by cleaning the pistol properly, then with the pistol dis-assembled, place a round in the chamber and check if it goes in all the way with just light finger pressure.

Furthermore, even if the gunsmith is right about the cause of the problem that doesn't change the pistol into junk. Any real gunsmith should be able to shorten the barrel back face and the shoulder by one thread and deepen the extractor cuts a suitable amount, setting the barrel back one thread and thus eliminating the problem.

[vinmarvin]

Thanks as always guys. I noticed the small "step" between the chamber and the feedramp and I believe this is the "missing" piece the gunsmith saw. The theory about the chamber fouled up makes sense and that is where I'll start when I get back in SA. Feedback to follow.....

One of the reasons I value this site so much!!