Hammerli SP-20 Multiple Fires

[jjgun]

I have a Hammerli SP-20 that has shot flawlessly since I bought it. However, I recently started having a problem with multiple fires. It happens once or twice per 100 rounds fired. I cleaned the firing pin so it is not sticking. Does anybody have any suggestions as to the cause? Any suggestions would be greatly appreciated. I'd like to solve this myself as I'm in the middle of a bullseye league and can't afford to send the gun out and tie it up for a month or two. Thanks..........JJ

[Steve Swartz]

Troubleshooting mode here:

- What has changed?
- Same ammo, temperatures, conditions etc. in general?
- Obvious things to check; firing pin sticking (you already did that) what about firing pin broken, firing pin spring weak, etc?
- How is your trigger adjusted (creep/letoff/reset)

Is this truly a "slam fire" or a problem with sear/hammer engagement?

Steve

[mister G]

Highest on the most-likely list is the sear/hammer engagement. Something might be broken or the engagement is too shallow. You need to physically look at this.

[jjgun]

Thanks for the replies. Nothing has changed - same ammo, etc. I was thinking firing pin spring also. It would be the easiest fix. I'm going to clean it tonight and I'll check the hammer/sear. Haven't noticed anything in the trigger pull that would suggest anything different in the engagement. Didn't think about trigger adjustment. Good suggestions - thanks. 98 good shots, then 1 double fire?

[ASA]

..However, I recently started having a problem with multiple fires. It happens once or twice per 100 rounds fired...

I have a Walther GSP, bought 1983. Last year I started to have the same experience.
My local dealer fixed it but warned me it would re-occur after some time. and so it was: In May 2007 it came back worse then before. The help was a new triger unit.
The explanation of the dealer was: Over time the sharpness of the edges deteriorates. In my case "over time" translates into: it occurred after some 9,000 rounds. The temporary fix did last for approx. 2,000 rounds. With a new trigger unit I have fired some 3,000 rounds without any problems since.
(Standard pistol with CCI and Remington Target. The latter one was my favorite during the 80ies and 90ies, but the recent Remingtons have lower quality so I changed to CCi. BTW: the price for the ammo has risen considerably within half a year from 300 Euro per 10,000 to 420 Euro per 10,000. Is it the same in other countries?)

best regards

Axel

[randy1952]

I had a similar problem with my SP20, where it got to the point it was going full auto on me. Larry's Guns diagnose the problem as a head space problem. The face of the barrel chamber had flattened out enough from the bolt going forward enough that there was no head space left. I had to buy a new barrel to fix the problem.

[Richard H]

I've also seen this with broken firing pins, the pin is broken and the front half can move sometimes it will hang-up on the rear part of the broken pin and when the bolt goes forward the pin is jammed forward and fires off another round and this can happen very randomly.

It looks like everyone has given you a bunch of thing to look at, I'd start with the easiest cheapest first and work my way through.

[K38]

I would get hold of Larry at www.larrysguns.com he is a trained Hammerli tech and knows the guns well.

Dwight

[AIG1]

Hi JJGun, did you figure out what the problem with Sp20 multiple fires was? I am experiencing the same issue currently ( a double shot ~100 rounds or so) and I am running out of things to tweak. My casings have firing pin marks so I do not think I have head-space problem. The gun used to double fire once per few thousand ronds when I bought it used. now it has gotten much worse. I recently replaced the bolt and firing pin. I tried increasing the sear engagement (tweaking screw #15 counter-clock wise) and it did not solve the problem. I just increased the let off point (screw 35) while keeping trigger weight at 1000g. I hope that helps.

I completely disassembled the trigger mechanism (except removing the sear) and cleaned it up. The edges of the sear seem smooth, but the surface of the middle pivot that engages the sear seem a bit chewed up (small marks visible under the light).

I will contact larry at larry's guns as well. thanks for any comments.

I really like the gun and I hope I can get few more years of reliable service from it.

Alexi