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I finally got to test fire my SA42 over the weekend. Although previously I was successful in popping 10 or more hard primers in my garage, imagine my frustration when it failed to fire with the first shot of live ammo.

First, we tried one round of 1935 dated German 8mm. It dimped the primer but did not go off. We chambered the dimpled round again and it fired and ejected.

Second we tried one round of Romanian 8mm. It also FTF.

Third we tried one round of Yugo 8mm. Also FTF.

We tried one round of my own 8mm reloads. It fired, ejected and fed the next round in the belt which was a dummy round.
Then We tried 2 8mm reloads. The gun doubled. Both ejected clear and fed the third (dummy round again).

We opted to not try anymore reloads because it obviously slamfired.

We decided to rechamber the dimpled Romanian round with the dimpled Yugo round next in line. It fired the Romanian but did not slam fire the Yugo.

It refused to fire anything else so we gave up and returned home.

We tried popping primers in the garage again and had the same FTF results.

Since then I have tried trimming a little more length off the back of my firing pin so the hammer would strike the pin a little more forward..........no help.

I thought maybe the ejector spoon was putting pressure on the washers I brazed onto the pin. So I removed the ejector spoon and tried popping primers without it and still it failed to fire.

After removing the firing pin spring, it pops every primer I try with the first hit.

I think I might try swapping hammer springs with my ar15 to see if I get better results.

Suggestions anyone?

well I know pirate doesn't like the ar fcg but do you have a high performance hammer spring?, mine did the same as yours so I am going to pirates new bolt design to see if it solves the problem just need time to shoot

Make sure the hammer is moving freely and that you firing pin(s) slide easily. I had trouble with the flat ejector bars slowing the firing pin so I went with one of the yugo old style/round ones and it made a world of difference. You can also bend the legs of the AR hammer spring to get more tension to the hammer.

Make sure your bolt extension is recocking the hammer and the disconnector is engaging to try to figure out the doubling issue.

Intruder, make sure your gripstick fits tight. any play results in a loss of power to the
firing pin. Also any binding to the fp will be a problem. the straight style ejector extensions
cause binding, the spoon shaped ones are better. Alos as Tom reccommended use a heavy
ar hammer spring. personally I feel tha ar setup is marginal at best and any extra
spring tension should help. last lube your firing pin with some good GI LSA.

My gripstick fits tight. It has no play at all.

I am using the WW2 spoon type ejector.

I will try a heavy hammer spring and report back the results. But in the meantime I will try to bend the legs of the existing spring to see if I get more tension out of it.

For the doubling problem I did verify that the hammer/disconnector are working properly. I was able to simulate the slam firing by allowing the bolt to slam closed on a 8mm shell loaded with a commercial Winchester standard primer. I was thinking I should maybe shim the FP spring with washers, but shouldnt that make it even more difficult to fire the hard-primered ammo?