QBZ-191's Bolt Carrier Group.
Posted by chroniclad@reddit | ForgottenWeapons | View on Reddit | 18 comments
Posted by chroniclad@reddit | ForgottenWeapons | View on Reddit | 18 comments
Sinistrial_Blue@reddit
4-lug rotating bolt, I think.
Not sure what the lever at the top is?
Ritterbruder2@reddit
The Tavor 7 has something similar. It keeps the bolt in the forward (unlocked) position when out of the gun. That way, you don’t have to pull the bolt head out before reinstalling (like you do on an AR).
It’s just added soldier-proofing.
Wrangel_5989@reddit
It’s not soldier proofing although that can be an unintended added benefit. This keeps the bolt from locking prematurely, it’s called an anti-preengagement mechanism.
In the AR-15 and AR-18 the way the bolt head is prevented from locking prematurely is really stupid to be honest, it has the cam pin run along a track in the receiver until it reaches the end of travel. That’s what that little hump on the side of AR-15 uppers is for. This is bad already because it causes an insane amount of friction, but it’s even worse because the AR-15 receiver is made out of aluminum while the cam pin is made of steel so it wears out the receiver even faster. SIG created a “remedy” to this in the MCX by introducing a replaceable track where the friction is the highest and therefore the receiver wear is the worst.
However the solution to this can be done for cheaper and a lot simpler. In the case of the tavor the cam pin is held still by a rod until the bolt head needs to start rotating. In the case of the AK and Garand a shelf was machined into the cam track that kept the bolt from rotating until a starter lug was hit by a cam track in the trunnion that forced the cam lug out of that shelf to allow rotation.
In this case it seems inspired (loosely) by the ARX-160. The ARX-160 had 3 problem’s with anti-preengagement:
To solve that Beretta added a pin inside the bolt carrier and a small metal track in the receiver. That metal track holds the pin down, which prevents the bolt from rotating, until it’s time for the bolt to rotate at which point there’s an incline in the metal track that allows the pin to go up which allows the bolt to freely rotate.
Here in the QBZ-191 that pin is replaced by a lever because instead of a normal recoil spring assembly the Chinese went with an AR style buffer tube and AR style bolt and carrier but not T shaped charging handle. Instead of locking the bolt here it locks the cam pin, preventing it from moving which prevents the bolt from moving. Honestly a pretty good design all things considered.
littlelegsbabyman@reddit
Man. I wish experts or knowledgeable people got more upvotes. Since Reddit got popular it’s harder to find.
Makky-Kat@reddit
Huh I learn something every day, although that seems like an excessive amount of soldier-proofing. (Granted, if you have an AR bolt in the wrong position you can’t get it very far before realizing you did something wrong.)
Ritterbruder2@reddit
Alright, I had to do a bunch of weird shit to misassemble it.
The firing pin is spring loaded. The same spring pushes the bolt forward. I had to remove that spring.
I also had to take out the trigger pack. Otherwise the bolt lug will snag on the hammer.
Ritterbruder2@reddit
On an AR, you realize something is wrong because the cam pin hits the receiver when you try to reinsert the bolt carrier.
The Tavor 7 is weird. It has a bolt that can be rotated 180° for either left-hand or right-hand eject. The cam pin is tucked away inside the bolt carrier. There wouldn’t be anything to tell you that something is wrong.
You could in theory depress this lever arm, collapse the bolt body, and misassemble the gun. But that lever takes a ton of pressure to depress. You’d have to really try to screw it up.
In fact I’m going to give this a try now and report back, lol.
Sinistrial_Blue@reddit
Got it, makes more sense than cam-actuated OOB safety!
yuvalbeery@reddit
Anti bounce device. Some guns have gone with a tube in the bolt that has loose metal powder to solve this.
IVEMIND@reddit
Couldn’t you get really fancy and use a sodium-filled bolt like a valve on an ice? 🤔
CatEnjoyer1234@reddit
https://www.youtube.com/watch?v=bjsQ--XSviY&t=1800s
Anti pre engagement mechanism
Q-Ball7@reddit
It’s not really added soldier proofing.
While it is true that it keeps the bolt forward when out of the gun, it also keeps the bolt forward when the gun’s cycling.
This means that the cam pin isn’t wearing the receiver like it does on an AR-15 (which is why the MCX has that replaceable track on the left side), which in turn will make the rifle last longer.
BusterCharlie@reddit
Iirc the Remington model 8 uses a similar lever to lock the bolt in the unlocked position until it's ready to turn into the barrel extension, the m82 .50 cal rifle barrows this feature from the model 8, and I assume so does this rifle. The model 8 has a lot of features later guns copy, see the Kalashnikov safety/dust cover
Ritterbruder2@reddit
I see, that makes sense. Is the cam pin really recognized as a weak point in the AR design?
Q-Ball7@reddit
Yes. It's only an issue at very high round counts though.
Here's everything you'd want to know about the QBZ-191.
PossiblyAKnob@reddit
This video explains the advantages of this type of setup.
https://www.youtube.com/watch?v=B3-vEiMeYlM
LeoLi13579@reddit
Damn, cabbage was basically right
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