Topic: Unexpected problem with assault rifle

[Stojan Kostic]

Recently we received for review automatic rifle CZ M-70. The gun was allegedly fired 30 rounds itself without any external interventions, including pressure on the trigger. The weapon was dismantled and examined in detail, with no defects were observed. We even tried to get stuck firing pin but it just did not work. Since inspected weapon is practically copy of AK-47, did someone face with such a problem and if did not, what could cause such a malfunction.

Thank you in advance

Stojan

[afss]

Hi Stojan,

Usually when a weapon fires automaticaly, it hapens because something distrupts the operation of the disconnector.
In a normal operation, it is the finger of the shooter which presses the triger, in an excidental shooting it is something else.
I encountered a semi-automatic pistol (I can not revele the model) which fired automaticaly the moment it was chambered!
The reason was a manufacturing mistake which caused one of the parts to press the disconnector, when it was assembled in a wrong way.
In your case it could be the same problem (and you "fixed" it after disassembling & assembling it back) or just a piece of dirt stuck in the wrong place.

[Steve Scott]

Years ago, had an AK or SKS that did that.  It was brand new, still with Cosmoline packed inside the action.  Two teens took Dad's rifle down to the gravel pit, loaded and inserted the mag.  When they let the action go forward, the rifle began to fire full auto, with nothing touching the trigger.  The boy holding the rifle dropped it and ran (as did the other one), and one of the boys was hit in the side (non-life threatening, but hurt like heck!!).  When I examined the gun, I found nothing externally that would indicate this could happen, but when I repeated their steps, it fired full auto!!  Disassembly proved only that it was packed with Cosmoline for shipping/storage.  When reassembled, I could not get it to repeat.

[afss]

  It was brand new, still with Cosmoline packed inside the action.    Disassembly proved only that it was packed with Cosmoline for shipping/storage.  When reassembled, I could not get it to repeat.

I can only guess that the Cosmoline was "holding" the disconnector in an Auto mode. When you disassembled and reassembled the weapon. it became free and returned to behave like a "normal" weapon.

[Dwight Deskins]

I can only guess that the Cosmoline was "holding" the disconnector in an Auto mode. When you disassembled and reassembled the weapon. it became free and returned to behave like a "normal" weapon.

With no observed alterations or defects, this may be a likely cause.  But always do your comprehensive functional testing first.  If detailed disassembly of the firearm proves necessary, it can always be done later.   

I worked a similar case long ago.  In mine, the firearm (it wasn't an AK type) operated automagically simply due to improper assembly.  If I'd have took it apart and put it back together (with the parts in the proper configuration of course), I'd have still been scratching my head!

[Steve Scott]

LOVE the new term!!!!  Auto-magically....

[afss]

In mine, the firearm (it wasn't an AK type) operated automagically simply due to improper assembly. 

I had two cases of semi-automatic weapons that became fully automatic:
1. A pistol that one of its parts was assembled improperly.
2. A shotgun that was assembled wrongly on its holding device.
In both cases, after the problem was recognized, it was solved.

[Stojan Kostic]

With some delay, thank you guys for all answers,
Lior, your suggestion with disconnector is good, but problem with this part led to the next problem with triger which must be pulled or blocked in rear (firing) position. Failure of two important parts in AK-47 theoretically is possible but practically, unlikely. Steve also had very good suggestion because I also found traces of some conservation lubricants, but unfortunate, I can't replay shooting incident.
Sincerely, Stojan
 

[afss]

The main thing one should take from this case (and all the other cases described) is allways be carefull with weapons you see for the first time.
Never point then in the direction of someone or to hard surface.
Allways point them into an absorbing target.
And expect the unexpected!

[Qendrim]

Hi
I had one case like yours, but in that CZ M70 AB2 (AK47 copy) which I did examination, we found that firing pin was blocked. So, you have just to put the magazine into the gun and try to load. When the bolt is released, all amunition will be fired automatically.
Sincerely,
Qendrim

[Stojan Kostic]

Thank you Qendrim,
My conclusion is also that the firing pin had to be blocked if this case report is true. Unfortunately, I can't  prove it, because the blockade is probably due to a temporary accumulation of observed old and dry conservation grease in fire pin hole. I think this is the most logical explanation for now.

[winterh]

On the AK-47, AK-74 and various clones, the hammer has two sear surfaces, one on each side of the hammer. The trigger also has two sear hooks, one on each side of the trigger, in the middle (and operating independently is a disconnector hook that catches rhe hammer and holds it to the rear when the trigger is depressed, allowing for semi-auto operation. If something restricts or intefears with the disconnector hook the weapon may go full-auto, however,if you release the trigger the hammer will remain to the rear. As the trigger and the disconnector are two seperate parts, controlled by the same spring sets, malfunctions of the type you describe are rare but not unheard of. Trash in the firing pin recess is most often the culprit...HW