View Full Version : Can you repair peening on a breech face?
May 19, 2009, 11:43 PM
I have an IZH 35 22 caliber target pistol that's starting to show peening on the face of its breech. This is a known problem w/ these pistols.
At this point it's doubling with certain brands of 22 LR ammo (e.g. Jagd Pistol Match), but this behavior is sporadic. My suspicion is that the peening is causing a headspacing problem.
What I'm wondering is whether there's an effective repair for this. Can the peened surface be restored, and maintain its integrity?
Alternatively is there a technique for adding metal and then forming this to maintain the proper headspace.
This is an IZH 35
May 21, 2009, 03:29 AM
Adding metal and forming would most likely require welding and machining. Problem is, the heat created from welding also changes the hardness of the metal. Too much heat with improper cooling could make big chunks break off next time instead of just peening.
"Do not make parts if you can buy them"- a wise old gunsmith to an apprentice
May 22, 2009, 10:28 AM
I know that that's sometimes a problem w/ welded-up lugs - they can apparently become brittle and shear off.
So if you reform a peened edge, is there anyway to heat-treat the metal to restore its hardness?
May 26, 2009, 08:08 AM
Proper cooling will prevent over-hardening and brittleness. Someone who knows more about metallurgy than me will have to explain the details.
May 26, 2009, 10:57 PM
I am not familiar with that pistol, but this is what has been done with other guns. Drill out an area of the breech face (centered on the barrel, not on the firing pin hole) larger than the base of the cartridge case. Tap the hole, and install a hardened, threaded plug. Drill a new firing pin hole and refit the firing pin as needed. It requires a lot of careful work and will cost money, in addition to the possibility of ruining the pistol, but it has been done and it will work if feasible.
May 27, 2009, 01:26 AM
If the peening hasn't progressed too far, this tool might work...
May 27, 2009, 09:16 PM
I don't know this handgun,and I am an ameteur at being a smith,but I did do a lot of work on plastic injection molds,and they have similar issues.
It is a .22 I assume blowback.No locking lugs.Headspace is in the breech counterbore,yes?
Consider this.Strip the slide,have it placed in a good,square toolmakers vise like my Herman Schmidt,and just dust off the face of the slide.If there are low spots battered in somewhere,leave them if they are only cosmetic.Remove the least material possible to establish a square slide face and also reduce the headspace in the counterbore to maybe .001 less than minimum.Then,with the proper size end mill,recut the breech face,and stone the high spots off the tool finish.
Assuming we are talking about .003 or so? (My speculation) it might work fine.
To consider first: How the disconnect will feel about it,and the cosmetics of how the rear of the slide and frame will look match polished.
Hopefully,this is not about the firing pin hitting the edge of the chamber dry firing.Different ball game.
I'm not looking at the parts,so this is just for ideas.
May 27, 2009, 10:27 PM
That will work for a while. But if the slide is soft, as I suspect, the peening will continue and will soon become obvious again.
Your thought about it being it cosmetic is a good one, though. It is quite possible that the peening will proceed to a point, then stop as the metal is compressed. That is often the case with both battering and wear on guns; the owner panics on seeing the damage to his new gun and does more damage trying to correct the problem than could ever have been done by simply ignoring it.
May 28, 2009, 04:01 AM
A couple more things I thought of..
Before even thinking about cutting,stick a test indicator in a height gage and set the slide up verticle and measure!!High spots,low spots,slide face to boltface(headspace).Use that data to make decisions.
If a person did dress the boltface.the firing pin tip would move forward,toward the edge of the chamber.Cotton picking rimfires can be finnicky here
The other info is,with the exception of a porous material,and maybe an MIM part would be porous,compression does not really occur.Displacement occurs.A low spot one place makes a high spot somewhere else.
Having said that,I have certainly obseved,and fixed,mold parting lines that were horribly beat up from clamping up on plastic.
I'm talking 41xx steel in the Rockwell 30's being displaced by plastic,because the plastic,like hydraulic oil ,is not compressible,either.
I think maybe even bullet lube on the bolt face could be a problem.Keep the bolt face clean.
May 29, 2009, 09:22 PM
Thanks for the feedback.
The peening is actually apparent on the external edges of the breech face, not around the chamber rim where you'd expect to find it. This is a known issue w/ the IZH 35's, that crops-up with certain series of these pistols. They're Russian made target pistols and the quality of their metallurgy has varied over the years. On the affected pistols, peening will occur on either the breech or bolt faces.
I'll try to take a few pictures to post that depict what I'm describing. But I think that what happens, rather than a deformation of the chamber rim, is that the breech face itself spreads out which results in rounds not fully chambering.
But the affect is very subtle, at this point. I don't tend to encounter problems until I've shot maybe 50 rounds in succession. So it may be that heat is a factor.
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