Help Me Troubleshoot AR 9mm Issue

[SJG 253]

So, I am out of State and Purchased A Brigade 9mm AR style carbine. She runs fine except the bolt will not stay open on the last round fired which according to the manufacturer it should. I send it back to the mfg and they returned it to me in 2 days after they said they fixed it. Well it still will not stay open when the last round is fired. This rifle does not have a DI system, it is a blow back  I assume. It is designed to work with Glock mags and I have tried several but it will stay open on the last round fired even with different Glock mags and different 115 grain 9mm ammo. Today, I installed a CMC Single stage flat  trigger and upgraded the charging handle. The trigger works fine and I assume that neither has anything to do with the problem. I tried it with the original charging handle and that did not make a difference. So my question is, how do I go about trying to figure out what the problem is in a non DI system?. I just want to see if I can resolve this myself without having to send it back again.

[High Exposure 5,661]

Pics of the LRBHO system?

There are a few different types from a few different manufacturers.

Some types can be very temperamental.

There is no gas system to tune so experimenting with springs and buffers tailored to your ammo will likely be the key.

trigger, charging handle, etc... should have no effect on the ability to LRBHO.

[SJG 253]

see attached videos

[High Exposure 5,661]

Yeah. That’s not right.

You already sent it back and they said they fixed it? I call bullshit.

I would return the gun and ask for a refund.

That LRBHO design is not working for shit.

The bolt looks like it was made by a beaver. Look at all those roll marks on the ramp. Doesn’t look like a Glock bolt either.

I would be pissed if that was my gun.

[SJG 253]

Texted mfg and also called and left message. Will call them tomorrow also.  Let's see what they say. They are 45 miles away from me. 

[Low Profile 9]

I believe the problem with most of the ar style 9mm guns lrbho, is primarily due to the small bolt diameter and shape. Even with the bolt catch raised all the way up, it only has a very small interface with the bolt face. I have a problematic MM 9mm carbine.

[SJG 253]

The bolt diameter and shape is larger not smaller than a standard AR-15 bolt

[Low Profile 9]

Perhaps I was not Clear, the lugs on the front of a typical ar bolt are engaged by the bolt catch, the blow back 9 does not have these and the bolt face in essence is smaller. look into your ejection port with a light when your bolt is locked back and I think you will see a minimal engagement.

[Low Profile 9]

Perhaps I was not Clear, the lugs on the front of a typical ar bolt are engaged by the bolt catch, the blow back 9 does not have these and the bolt face in essence is smaller. look into your ejection port with a light when your bolt is locked back and I think you will see a minimal engagement.

[SJG 253]

13 hours ago, High Exposure said:

Yeah. That’s not right.

You already sent it back and they said they fixed it? I call bullshit.

I would return the gun and ask for a refund.

That LRBHO design is not working for shit.

The bolt looks like it was made by a beaver. Look at all those roll marks on the ramp. Doesn’t look like a Glock bolt either.

I would be pissed if that was my gun.

They are sending me out a new bolt and a new Glock fun stick to see if the problem gets resolved. If not, they they want me to send back the lower again. They did send me a video of the test they did after they fixed it and it did hold open. In the test they loaded the mag with five rounds, they used the same brand ammo I used and the same type mag it came with. The guy said something about something on the lower catching or not catching to hold the bolt open on the lower that they adjusted, based upon the video can you explain to me what it is on the lower that they are talking about?

[Low Profile 9]

the square arm that you are manipulating in your video actuates the bolt catch, when the tab on the other end, which protrudes into the mag well contacts the follower in the Glock mag when it rises after the last round. sometimes this tab needs to be adjusted.

 

[SJG 253]

Yeah, that tab is what they said they adjusted maybe not enough? But in the test video of the fix, they did get the bolt to stay open using same ammo and mag that I used. Now it will not stay open

[Zeke 5,504]

51 minutes ago, SJG said:

Yeah, that tab is what they said they adjusted maybe not enough? But in the test video of the fix, they did get the bolt to stay open using same ammo and mag that I used. Now it will not stay open

Tab bent again dude 

[Low Profile 9]

On my carbine, I have bent the tab to lift the bolt catch as high as possible, but the contact area is still very small. LRBHO is better but inconsistent and the bolt catch is wearing and deforming in the area of contact. IMO the heavy 9mm bolt and its shape are the main culprits. Mag spring tension and follower shape can be factors also.  Im not sure it can be corrected, sad to say as it is designed.

[SJG 253]

Could be. They are sending me a new bolt and brand new mag to try. Strange thing is that when i put mag in lower only with or without round, it appears to correctly lift and move the catch, as it should or should not. But when I put the upper on and slingshot the bolt with a mag in and no round, it does not stay open. I have read somewhere that some people claim that installing a Magpul Bad Lever can correct the problem, but I not sure why?

[High Exposure 5,661]

In my experience the BAD lever (I hve them on almost all of my ARs) exacerbated the issue as the extra weight on the bolt catch made it harder for the mag spring to push the follower up and lock the bolt to the rear.

[Low Profile 9]

Very little engagement with the bolt catch on my gun = no catchy some times

[SJG 253]

Got the new bolt and mag from the mfg and installed it. It now locks open, at least when I charge it with empty mag in. Will test at range on Thursday.

[Zeke 5,504]

@High Exposurewhat is the gtg 9 kit for ars soo I may not experience the OP’s problem in the future?

[carl_g 568]

33 minutes ago, Zeke said:

@High Exposurewhat is the gtg 9 kit for ars soo I may not experience the OP’s problem in the future?

A CZ Scorpion pistol. You can keep it at my place lol!

[High Exposure 5,661]

35 minutes ago, Zeke said:

@High Exposurewhat is the gtg 9 kit for ars soo I may not experience the OP’s problem in the future?

I love my QC10. Took some train and error to get running, but it has been boringly reliable once I got the buffer system dialed in.

Just now, carl_g said:

A CZ Scorpion pistol. You can keep it at my place lol!

I really wanted one, but I have seen four of these carbines self destruct at steel comps. It does not inspire confidence.

[Zeke 5,504]

2 minutes ago, carl_g said:

A CZ Scorpion pistol. You can keep it at my place lol!

Can I live in your basement?

[carl_g 568]

12 minutes ago, Zeke said:

Can I live in your basement?

that’s my kids’ domain... No

[Tony13 59]

13 hours ago, Zeke said:

@High Exposurewhat is the gtg 9 kit for ars soo I may not experience the OP’s problem in the future?

Joe Bob Spartan which is rebranded New Frontiers upper and lower. Running Foxtrot Mike BCG with buffer and spring. Probably 4k rds thru it with zero problems.  Shot 3 matches with it already.