Author Topic: CZ Scorpion Out of Battery Detonations  (Read 2098 times)

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Offline MeatAxe

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CZ Scorpion Out of Battery Detonations
« on: December 09, 2023, 10:24:44 PM »
Apparently, this is a thing, that I wasn’t aware of until now:

https://m.youtube.com/shorts/yD0TjXFvkuY

Seems to be brought on by rapid fire / binary triggers and soft metal of the OEM bolt and firing pin block, or the firing pin block otherwise failing:

 https://m.youtube.com/watch?v=1t220BqjCYs

https://m.youtube.com/watch?v=UV7bkJXoOnw


« Last Edit: December 09, 2023, 10:44:35 PM by MeatAxe »

Offline cavegeo

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Re: CZ Scorpion Out of Battery Detonations
« Reply #1 on: December 10, 2023, 09:09:20 AM »
OOB firing with blowback firearms has always been an issue. 

This is why ammo manufacturers that make aluminum cased ammo typically have a disclaimer to not to use aluminum case ammo in blowback firearms.

This is why blowback firearms had fallen out of favor for breach lock firearms after WWII.

With the exception of open bolt full auto firearms most modern firearms use a locking mechanism as they tend to have less issue though they are more expensive to manufacture as customers have migrated to modern firearms having a greater safety factor when compared to blowback. 

That is not to say that all blowback firearms have been discontinued but the majority of currently available blowback firearms tend to be in smaller calibers like the 22 LR or 32 ACP.

Very few modern firearms have been designed that use Service Calibers such as the 9mm since WWII due to the greater safety afforded to breach lock firearms. 

Offline Wobbly

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Re: CZ Scorpion Out of Battery Detonations
« Reply #2 on: December 10, 2023, 09:47:55 AM »
Just what I've been saying...

The firing pin blocks on any auto pistol are not always completely Stop or Go. (That is thinking brought on by living in the Digital Age.) Due to mechanical tolerance stack-up, there is going to be a "gray area" in between the 2 states. So instead of being a 50/50 proposition, it's going to be something more like 49/49, which leaves 2% error. It's that tiny error space that we are discussing.

This is usually not a problem. If the hammer or striker is allowed to start falling early, then while the hammer is still falling the bolt is allowed extra time to move into it's final battery position. Thus due to the inertias within the system, the bolt is securely closed before the firing pin can strike the primer, which then starts the powder to burn. There is time lag in the hammer fall, and there is more time lag in the ignition sequence.

But anything that upsets that delicate timing sequence, anything that consumes those few milli-seconds of time... like dirt in the chamber, or out-of-spec ammo having to be forced home... could allow the ammo to fire OOB.

The higher the rate of fire, the more imperfect your ammo, the more slop in the mechanical tolerance, the more lax in your cleaning standards, then the greater chance for trouble.


I'm not saying there wasn't undue wear present on his firing pin block. That's not it at all. What I'm saying is don't look so surprised! Due to the way the simpler mechanical interlock systems work, this can happen on almost ANY auto pistol/rifle.
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Offline MeatAxe

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Re: CZ Scorpion Out of Battery Detonations
« Reply #3 on: December 10, 2023, 02:48:10 PM »
Although these detonations in the Scorpion are not all that common, apparently, it just goes to show that you need to check the condition and maintain your weapon periodically, especially if you’re using a binary trigger, bump firing, etc., a lot, which is risky in all semi auto weapons, not just blow back operation. AKs and ARs have OOBDs too.

Like the guy was saying, the addition of a safety sear would make these a lot safer. But, of course, for whatever stupid reason, safety sears — AKA “auto sears” to the atf — are strictly verboten in a semi auto weapon. Which is why the atf created the infamous  semi auto AK with a “third pin” for a safety sear to entrap unsuspecting citizens unknowingly possessing “machine guns.”

Offline briang2ad

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Re: CZ Scorpion Out of Battery Detonations
« Reply #4 on: December 11, 2023, 02:27:04 PM »
Although these detonations in the Scorpion are not all that common, apparently, it just goes to show that you need to check the condition and maintain your weapon periodically, especially if you’re using a binary trigger, bump firing, etc., a lot, which is risky in all semi auto weapons, not just blow back operation. AKs and ARs have OOBDs too.

Very true.  A couple of points:  No, its not an MP5 - a very proven, roller delayed icon used by many militaries.  But the Scorpion evidently passed enough tests to be used in Serbia, Bosnia and Herzegovina, Hungary, and the Czech Republic as a standard-issue firearm, along with it being used by Argentina, Ukraine, and Finland, among other countries.  Now maybe the full auto with appropriate sear makes it a moot point, but I see its extensive military and police use as risk reduction for us chickens using semi-auto...

As long as we keep things half-way smart:  Next point.   I don't use or need a binary trigger.  I keep the standard trigger pack in and only mod the trigger itself and the reset spring - which gives me a lighter pull but doesn't bump fire/etc. 

I think stepping out with too much aftermarket on the trigger is dumb - especially with blow backs.  Its a great home defense gun largely as is.  Tai Chi is bad for everyone. 

And yet at the same time... HK went straight blow back with their UMP - as their latest tech for their "truly modern" approach to this type of gun.

https://hk-usa.com/hk-models/ump45/

« Last Edit: December 12, 2023, 12:01:59 PM by briang2ad »