Early SP-20 slam fires
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Earlyriser
- Posts: 31
- Joined: Fri Nov 25, 2005 7:52 am
- Location: Central NY
Early SP-20 slam fires
A chronic case of doubling has worsened despite attempts to correct by several experienced gunsmiths. By chance, I retrieved a fired case after doubling and found no indent from the firing pin. Three doubles later the fired cases had no indentations. Then the gun fired as the slide was released. An examination by the gunsmith, including chamber check with 22 Cal reamer, found nothing. Has anyone ever had a similar experience?
If the chamber depth is correct and the round chambers flush then I'd check the bolt. Is it possible the depth of the recess where the round goes was marginal to begin with and the bolt face has flattened enough over time to cause the round to go off?
Certified Safety Instructor: Rifle & Pistol
They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.
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They that give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.
~ Ben Franklin
Doubling
I had a similar problem with my IZH-35.
Another poster suggested that I run a sharp point or pin punch over the bolt face to check for burrs. I could not see any burrs, but I sure felt some with my pin punch. The burrs were right on the bolt face around where the firing pin comes through the bolt face.
A little work with a Dremel tool and a small grinding point and I was able to every so slightly round the area where the firing pin came through the bolt face. Reassemble and test fire. No more doubling.
If you do not feel comfortable doing this, any gunsmith can do this, if they know what to look for.
The big clue is that you did not see any firing pin marks on some of the brass. There is a burr somewhere, that is firing off a round every now and then. These burrs are very difficult to see even with a magnifying glass. You have to feel the burr to find it.
Another poster suggested that I run a sharp point or pin punch over the bolt face to check for burrs. I could not see any burrs, but I sure felt some with my pin punch. The burrs were right on the bolt face around where the firing pin comes through the bolt face.
A little work with a Dremel tool and a small grinding point and I was able to every so slightly round the area where the firing pin came through the bolt face. Reassemble and test fire. No more doubling.
If you do not feel comfortable doing this, any gunsmith can do this, if they know what to look for.
The big clue is that you did not see any firing pin marks on some of the brass. There is a burr somewhere, that is firing off a round every now and then. These burrs are very difficult to see even with a magnifying glass. You have to feel the burr to find it.
It can also be caused by a stiff or binding extractor. It does take particularly touchy ammo to slam fire like this. I had one Benelli that was fine with RWS, but would double quite often with CCI. The problem was inadequate headspace due to the breech being beaten down after many thousands of rounds.
had this happen to a teammate last week in germany. was a pardini that belonged to the amu. not sure what he did to get it working again. can't remember if he put his grip on another gun and finished in the next relay. I know it made me finally order a backup gun like I have been saying I needed to do for the last several months. Stinks to loose pts due to gun issues but even worse to get a DNF. Despite his zero and what we think was a target malfunction zero, as a team we finished second.