Uzi/HK safety question

[Ron3]

Are the HK mp5-type or Uzi - type semi-auto's drop safe?

The Beretta CX4 is supposed to be as is the ARX100. An AR - type isn't, an 870/500/590 shotgun isn't either.

So how about the closed-bolt semi auto Uzi and HK mp5 pattern guns?

[militarymoron]

Don't know about the Uzi, but I'd say 'no, theoretically' on the HK. The safety on the standard SEF non-ambi/burst trigger pack just limits the travel of the trigger. With the selector on 'S', and the trigger taken out of the equation, I can still drop the hammer by moving the front of the sear down (with a small screwdriver etc). It's against the spring tension of the elbow spring and roller though, so I have no idea what kind of drop would be needed to do it purely by inertia.

[SteyrAUG]

Depends upon the quality of the manufacturer. The HK94 is a "drop safe" design based upon the G3 and so long as you haven't modified it with something like a Williams trigger, the semi auto versions are basically as "drop safe" as the military versions. Of course I wouldn't want to extend that to every HK clone out there.

As for the Uzi, the semi auto versions might be more "drop safe" than the SMG given the open bolt vs. closed bolt design. The most vulnerable are probably semi auto conversions that lack the ratcheting top cover but feature a fixed firing pin on the face of the bolt. Semi auto only versions have a captured firing pin that seems like it would be drop safe, especially with things like the grip safety.

This is one reason I don't particularly care for aftermarket or tuned triggers on military or semi auto versions of military rifles.

[SteyrAUG]

Don't know about the Uzi, but I'd say 'no, theoretically' on the HK. The safety on the standard SEF non-ambi/burst trigger pack just limits the travel of the trigger. With the selector on 'S', and the trigger taken out of the equation, I can still drop the hammer by moving the front of the sear down (with a small screwdriver etc). It's against the spring tension of the elbow spring and roller though, so I have no idea what kind of drop would be needed to do it purely by inertia.

But how would you duplicate that with the pack installed? The drop safety requirement is why the HK has a heavier trigger pull than other designs.

Hate to say it but I've seen way too many guys fumble a factory MP5 at ranges with hard decks, usually with the safety OFF but I've yet to see one actually discharge. These were all LE incidents so when I say way too many, I've seen it about half a dozen times.

You could easily test it with just a SEF pack with the sear trip engaged and see if you can get it to release by dropping it ass end on a hard surface.

[militarymoron]

But how would you duplicate that with the pack installed? The drop safety requirement is why the HK has a heavier trigger pull than other designs.

You wouldn't of course. That's why I said 'theoretically', since the drop safety depends on friction (sear nose and hammer) and the elbow spring tension vs. a 'true' mechanical block. Empirically, I don't know. Obviously the right set of circumstances (shock/angle) would have to be present, and that may not happen within the design requirements.

Since you suggested it, I just tried it out on an SEF pack taken out of the grip assembly from a HK93. I taped the safety in the 'safe' position and put masking tape on the sides to prevent the pins from getting dislodged. I dropped it from about 4 feet onto concrete, and to my surprise, the hammer fell the first time! I checked the pins, and the elbow spring pin had dislodged slightly. I realigned it and tried it about 4 more times but the hammer didn't fall. I didn't want to bang up my trigger pack any more. It might have been a fluke that one time, and I really didn't expect that to happen. Maybe you can try it as well on an old one.

[Gunfixr]

In the uzi, the manual safety blocks the trigger, but the grip safety blocks the sear.
I have a semiauto uzi, but I built it myself, and maintained this. I also retained the ratcheting top cover.
I haven't looked in a factory uzi. The grip safety blocks the sear on the right side of the gun, but only the left side of the sear is used (fa guns have both sides). Depending on how imi or vector did it, the grip safety may or may not work as originally designed.

Sent from my SGP612 using Tapatalk

[SteyrAUG]

You wouldn't of course. That's why I said 'theoretically', since the drop safety depends on friction (sear nose and hammer) and the elbow spring tension vs. a 'true' mechanical block. Empirically, I don't know. Obviously the right set of circumstances (shock/angle) would have to be present, and that may not happen within the design requirements.

Since you suggested it, I just tried it out on an SEF pack taken out of the grip assembly from a HK93. I taped the safety in the 'safe' position and put masking tape on the sides to prevent the pins from getting dislodged. I dropped it from about 4 feet onto concrete, and to my surprise, the hammer fell the first time! I checked the pins, and the elbow spring pin had dislodged slightly. I realigned it and tried it about 4 more times but the hammer didn't fall. I didn't want to bang up my trigger pack any more. It might have been a fluke that one time, and I really didn't expect that to happen. Maybe you can try it as well on an old one.

I thought most drop tests were done with the weapon set to fire. I could see where a fire control group might fail, but I bet it would be more reliable installed in a SEF frame even if set on the fire position. I remember reading about Singapore doing drop tests on the 33 before they adopted it and it was something crazy like drops from 12 feet.

Maybe for your next video you could scrounge an old G3 pack and do drop tests onto a hard surface.

[militarymoron]

If it were me, I'd drop test a weapon on safe and fire. I don't know what the protocols would be for different militaries.
Do you remember where you read that Singapore adopted the 33? I've never heard of that before. I wonder whether it was a particular unit.

[SteyrAUG]

If it were me, I'd drop test a weapon on safe and fire. I don't know what the protocols would be for different militaries.
Do you remember where you read that Singapore adopted the 33? I've never heard of that before. I wonder whether it was a particular unit.

Scratch that, Malaysia. Those were the kits that came in with the S-O-U trigger groups. Read about the testing in Small Arms Review.

[Ron3]

Very interesting information.

I had my doubts about the HK weapons. But I wasn't sure how much the grip safety helped on a semi-auto Uzi. Especially the McKay Industries build.