Author Topic: Same problem as others with HBI hand guards  (Read 602 times)

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Offline Matt85

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Same problem as others with HBI hand guards
« on: October 30, 2021, 12:35:59 PM »
Figured Id post that I recently bought the 7.8" HBI hand guard and Im having the same typical problems that Ive read about on forums.

1. If I torque it more then 30 in/lb the receiver pinches the bolt carrier.

2. The bolts keep coming loose while shooting despite application of blue loctite.

Ive got some new OEM lock washers on the way and will see if it resolves the problem of them coming loose. I still wonder what the factory is torqueing these things to since Ive read 60-80 inches pounds from different sources but all of the above is too much torque for my rifle.

side note: Someone posted on Amazon that these other lock washers work so I ordered some of these as well: https://www.amazon.com/gp/product/B007VAW0M8/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Offline MeatAxe

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Re: Same problem as others with HBI hand guards
« Reply #1 on: October 30, 2021, 05:51:50 PM »
Figured Id post that I recently bought the 7.8" HBI hand guard and Im having the same typical problems that Ive read about on forums.

1. If I torque it more then 30 in/lb the receiver pinches the bolt carrier.

2. The bolts keep coming loose while shooting despite application of blue loctite.

Ive got some new OEM lock washers on the way and will see if it resolves the problem of them coming loose. I still wonder what the factory is torqueing these things to since Ive read 60-80 inches pounds from different sources but all of the above is too much torque for my rifle.

side note: Someone posted on Amazon that these other lock washers work so I ordered some of these as well: https://www.amazon.com/gp/product/B007VAW0M8/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Yep. Problems. CZ should have continued with the original “military” extended receiver of the Bren 2S, which is much more useful and trouble free than the “commercial” “hand guard” they contrived for the 2Ms, which is less useful, problematic and forces customers to spend $$$ to try to correct the problem and / or comply with 922r if converted to a rifle.

According to CZ USA Customer Service (way back when they were still answering their phones), the  correct torque spec is 64 in.lbs. for the hand guard screws.

There’s been a lot of discussion on here RE: the wisdom (or not) of drastically reducing the number of mounting screws and either drastically reducing or drastically increasing the torque values on the remaining screws from spec to hold the aftermarket hand guard on. Consider the whole structure is integral with holding the barrel / receiver / “hand guard” together…probably not such a great add on to the (often badly overgassed) Bren 2, at least IMO.

Yes, Nordlock washers of the correct size are used, available at Fastenal.
« Last Edit: October 31, 2021, 04:15:15 AM by MeatAxe »

Offline Matt85

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Re: Same problem as others with HBI hand guards
« Reply #2 on: November 07, 2021, 03:44:28 PM »
Well I tried a new set of OEM lock washers as well as some Loctite 2422 but sadly the bolts still came loose. I was even able to get the torque up to 35 in/lb (40 in/lb causes binding).

Near as I can tell the lock washers aren't biting into the fasteners allowing them to loosen. Perhaps I need to go back to the OEM bolts... this will be my next test.

-matt

Offline MeatAxe

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Re: Same problem as others with HBI hand guards
« Reply #3 on: November 07, 2021, 07:37:30 PM »
Well I tried a new set of OEM lock washers as well as some Loctite 2422 but sadly the bolts still came loose. I was even able to get the torque up to 35 in/lb (40 in/lb causes binding).

Near as I can tell the lock washers aren't biting into the fasteners allowing them to loosen. Perhaps I need to go back to the OEM bolts... this will be my next test.

-matt


As much as I don’t care for the (lack of) utility and ergonomics, eventually I went back to the OEM “hand guard.” At least we know that’s a rigid, factory engineered, integrated receiver / barrel / “handguard” unit, all screws torqued to the factory spec 64in.lbs. Also, with the HBi hand guard, I was getting some weird chamber blow-by symptoms when fired: thick streaks of powder residue down the lengths of spent cases, not present when shooting the OEM unit - not a good sign.
« Last Edit: November 07, 2021, 07:47:49 PM by MeatAxe »

Offline Doctor Castle

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Re: Same problem as others with HBI hand guards
« Reply #4 on: November 15, 2021, 04:01:00 PM »
What about the CZ manufactured 922r handguard? It looks like HBI's but is slightly different. I'm guessing it has the same problems because it also free floats the barrel I think. But has anyone tried it?

Offline Matt85

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Re: Same problem as others with HBI hand guards
« Reply #5 on: November 20, 2021, 02:22:54 AM »
What about the CZ manufactured 922r handguard? It looks like HBI's but is slightly different. I'm guessing it has the same problems because it also free floats the barrel I think. But has anyone tried it?

that's a good question, hopefully someone will chime in.

HBI has sent me a new set of bolts and washers which at least for the last 100 rounds appears to be working. Hopefully these continue to work and my problem is solved. The bolts are still only being torqued to 35 in/lb which shouldn't matter as long as they don't vibrate loose.

I find it a bit interesting that, before I contacted HBI I had put a new set of CZ OEM washers in and they didn't work with the HBI bolts (they came loose). Something in the combination of HBI bolts, CZ washers, and HBI handguard doesn't work reliably. I would like to experiment some but sadly I seem to have lost all my original CZ parts (handguard and hardware).

-matt

Offline Gunswillie

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Re: Same problem as others with HBI hand guards
« Reply #6 on: November 24, 2021, 09:03:29 AM »
When I installed my HBI rail, used the factory bolts and washers. After 400 rounds hasn’t moved.