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-   -   Well, crap... (http://glocktalk.com/forums/showthread.php?t=1453384)

WoodenPlank 11-15-2012 19:32

Well, crap...
 
When I went shooting last week, my SBR starting short stroking for no discernible reason. Everything was relatively clean, well lubed, and it had never had problems before. Unfortunately, I had no spare parts or tolls with me, so I was kinda screwed on troubleshooting.

I took it home that night and cleaned the crap out of it, and relubed everything. Couldn't find any worn or busted parts, so I figured that maybe it was chamber filth from the steel cased Tula.

This week, I hit the range again - same problem. This time, I had spares. I swapped in a carbine buffer in place of the H2, no joy. Swapped out the BCM bolt carrier group for a crappy, worn out DPMS, and the gun ran.

Whut?

Dropped the H2 buffer back in, gun still ran.

:dunno:

So, I swapped the BCM bolt into the DPMS carrier, and vice-versa. BCM bolt + DPMS carrier, and it ran. BCM carrier with DPMS bolt, no joy.

When I got home tonight, I started going over the BCM carrier. No obvious burrs or bad spots inside the carrier, so I checked the gas key. The staking on the front screw looked a little weak, so I checked the screw. One tiny bit of pressure later, and the damn screw turned.

To quote one of my favorite TV shows - "Well THERE'S your problem!"

So, I tried to tighten the screw down more...

and more....

and more....

This damn thing is stripped!

:steamed:

I can't get the screw out because of the staking, but the staking wasn't enough to stop it from spinning.

Lesson learned - Even BCM can screw (heh) up every now and then. I've only had this BCG for about 6 months, and it's only seen about 500 rounds (work has been a ***** lately), so it's definitely not due to use or abuse. I've already got an email in to them, so I guess it's wait and see to find out what they are willing to do to fix it.

Second lesson learned - it doesn't hurt to double-check gas key screws, even on bolt carriers from higher end companies. Just because it LOOKS staked doesn't mean it's really secured.

bmoore 11-15-2012 19:38

Well atleast you got the problem pinned down. Sucks that the BCM carrier failed, let us know how it works out with them.

LA_357SIG 11-15-2012 19:40

The sky is falling? :tongueout:

But anyway, I had to replace a gas key when I dropped it (a BCG) on a cement floor. I used new bolts and rockset that came with my AAC suppressor mounts. The reason I bring this up, is my clumsiness has given me an opportunity to test this staking debate. I put a little over 500 rounds through so far with no malfunctions. I only wish I would have made witness marks to have definite proof of if the bolts were unscrewing.

You have any interest in testing an unstaked gas key? Or try DSArms "key lock" gas key? Or are you content with staking?

WoodenPlank 11-15-2012 19:46

Quote:

Originally Posted by LA_357SIG (Post 19636223)
The sky is falling? :tongueout:

But anyway, I had to replace a gas key when I dropped it (a BCG) on a cement floor. I used new bolts and rockset that came with my AAC suppressor mounts. The reason I bring this up, is my clumsiness has given me an opportunity to test this staking debate. I put a little over 500 rounds through so far with no malfunctions. I only wish I would have made witness marks to have definite proof of if the bolts were unscrewing.

You have any interest in testing an unstaked gas key? Or try DSArms "key lock" gas key? Or are you content with staking?


If it gets fixed on my dime/headache, it's getting done right, and done overboard. Fortunately, I'll be seeing just the man for the job next weekend.

Then again, I get the feeling that BCM will be making it right.

vettely 11-15-2012 19:54

Interesting. Good information to know, just in case.

ithaca_deerslayer 11-15-2012 19:55

Is the hypothesis here that the screws stripped themselves in 500 rounds?

Or were they factory over torqued to begin with?

Was gas leaking out where the screws were supposed to be holding the gas key tight to the carrier?

Big Bird 11-15-2012 19:57

I had a similar problem with my LMT SBR upper when I first got it and it gave me fits. When I finally broke down and called LMT the first question out of the tech's mouth was what weight buffer am I running? Well, an H2 of course...everyone knows you should run an H2 in a Carbine length gas system right? Nope. LMT drills their gas ports to cycle with a standard weight carbine buffer. So I replaced the H2 with a carbine weight buffer and the stupid thing has run like a champ ever since. Never skipped a beat.

When gas keys are staked and things aren't perfect its not unusual to break off the bolt close to the carrier or just under the bolt head. BCM bolt carrier groups are made by fallible people using imperfect materials. Like all mechanical parts they have a failure rate...

WoodenPlank 11-15-2012 19:57

Quote:

Originally Posted by ithaca_deerslayer (Post 19636255)
Is the hypothesis here that the screws stripped themselves in 500 rounds?

Or were they factory over torqued to begin with?

Was gas leaking out where the screws were supposed to be holding the gas key tight to the carrier?

Over-torqued, and the carrier threads or screw threads gradually gave way.

I couldn't find any sure marks to show it, but I'm assuming gas was leaking out from around the gas key and causing the short-stroking.

Cole125 11-15-2012 19:58

I'm sure BCM will make it right, and send you a new BCG.

Just goes to show even "high end" parts can have issues.

WoodenPlank 11-15-2012 20:00

Quote:

Originally Posted by Big Bird (Post 19636261)
I had a similar problem with my LMT SBR upper when I first got it and it gave me fits. When I finally broke down and called LMT the first question out of the tech's mouth was what weight buffer am I running? Well, and H2 of course...everyone knows you should run an H2 in a Carbine length gas system right? Nope. LMT drills their gas ports to cycle with a standard weight carbine buffer. So I replaced the H2 with a carbine weight buffer and the stupid thing has run like a champ ever since. Never skipped a beat.

I've seen various reports on what runs best in the LMT SBR uppers. I run an H2 in mine since I shoot mostly 5.56.

In this case, though, the bad key meant the buffer didn't make a difference. I tried it with a C buffer, and no joy.

Made in Austria 11-15-2012 20:01

That sucks. I hope you get it fixed soon. I am sure that BCM will take good care of you. They will probably replace the whole carrier with a new one. I also hope that this problem is extremely rare. Just ordered my third BCM BCG last week.

WoodenPlank 11-15-2012 20:04

Quote:

Originally Posted by Made in Austria (Post 19636277)
That sucks. I hope you get it fixed soon. I am sure that BCM will take good care of you. They will probably replace the whole carrier with a new one. I also hope that this problem is extremely rare. Just ordered my third BCM BCG last week.

I have no doubt that it's a rare occurrence, honestly.

Matthew Courtney 11-15-2012 21:41

Quote:

Originally Posted by WoodenPlank (Post 19636262)
Over-torqued, and the carrier threads or screw threads gradually gave way.

I couldn't find any sure marks to show it, but I'm assuming gas was leaking out from around the gas key and causing the short-stroking.

It was obviously properly torqued as it was tested and inspected. BCM has the best quality control in the business. In addition, they use genuine buffalo fat as a rust preventing preservative. The failure could have only been caused by your wanton and reckless use of Slip 2000. BCM's website clearly states that the use of Slip 2000 voids any and all warranties because it reacts with the genuine buffalo fat to create an exothermic reaction which literally cooks the gas key bolts, evincing that they were properly staked and making them into a tender and delicious snack that can be enjoyed at the range with a little Hoppes # 9.

:wavey::tongueout::rofl:

WoodenPlank 11-15-2012 21:42

Quote:

Originally Posted by Matthew Courtney (Post 19636616)
It was obviously properly torqued as it was tested and inspected. BCM has the best quality control in the business. In addition, they use genuine buffalo fat as a rust preventing preservative. The failure could have only been caused by your wanton and reckless use of Slip 2000. BCM's website clearly states that the use of Slip 2000 voids any and all warranties because it reacts with the genuine buffalo fat to create an exothermic reaction which literally cooks the gas key bolts, evincing that they were properly staked and making them into a tender and delicious snack that can be enjoyed at the range with a little Hoppes # 9.

:wavey::tongueout::rofl:

You had me going for the first two sentences, actually.

After that, it all came off the rails. :tongueout:

Big Bird 11-15-2012 21:46

Quote:

Originally Posted by WoodenPlank (Post 19636271)
I've seen various reports on what runs best in the LMT SBR uppers. I run an H2 in mine since I shoot mostly 5.56.


In this case, though, the bad key meant the buffer didn't make a difference. I tried it with a C buffer, and no joy.

Call LMT. They will tell you exactly what I said.

You may get away with it in some rifles or may not. But my guess would be you are running it on the edge of reliability and when things get dirty or close to being out of spec it adds up.

Maybe not. I could be wrong. Been wrong before.

Honestly, Your BCG should still run with one screw tight as the key should still be tight against the carrier. But again, maybe not.

mjkeat 11-15-2012 21:48

Well I guess I can't say I've never heard of a BCM failure. Let us know how they handle it.

WoodenPlank 11-15-2012 22:16

Quote:

Originally Posted by Big Bird (Post 19636637)
Call LMT. They will tell you exactly what I said.

You may get away with it in some rifles or may not. But my guess would be you are running it on the edge of reliability and when things get dirty or close to being out of spec it adds up.

Maybe not. I could be wrong. Been wrong before.

Honestly, Your BCG should still run with one screw tight as the key should still be tight against the carrier. But again, maybe not.

It's not running. I can't *feel* any play in the key, but it's definitely not running. Bolt moves, just refuses to feed or lock back on empty.

As for the LMT bit, I was already considering dropping it to a Carbine carrier as a test. Once I get the BCM carrier un-buggered, I still plan to try it. Until the carrier failure, though, it was running perfectly even on Tula .223 with an H2 buffer.

Quote:

Originally Posted by mjkeat (Post 19636644)
Well I guess I can't say I've never heard of a BCM failure. Let us know how they handle it.

It's a first for me, too. Hoping to hear back from them by e-mail tomorrow.

bmoore 11-16-2012 09:17

Plank- can you give me some quick education on this. Do you think this is SBR specific? Or do you think it would have given way in any rifle? I am not to familiar with SBR.

Travclem 11-16-2012 09:29

Quote:

Originally Posted by WoodenPlank (Post 19636730)
It's not running. I can't *feel* any play in the key, but it's definitely not running. Bolt moves, just refuses to feed or lock back on empty.

As for the LMT bit, I was already considering dropping it to a Carbine carrier as a test. Once I get the BCM carrier un-buggered, I still plan to try it. Until the carrier failure, though, it was running perfectly even on Tula .223 with an H2 buffer.



It's a first for me, too. Hoping to hear back from them by e-mail tomorrow.

I have a factory 10.5" LMT. It has a semi auto carrier and a carbine buffer and is gassed to run in this configuration as per LMT. They say you might have issues with M16 bolt carriers and H/H2 buffers in their SBR uppers.

surf 11-16-2012 10:04

Recently installed fifty (50) LMT 10.5" barrels all with full auto carriers. All 50 run like a champ on standard H-Buffers. Indeed LMT designs the port size for this, however I will say that there are always anomalies and to run whatever works.

Travclem 11-16-2012 10:13

Good to know. All I know is what LMT told me.

WoodenPlank 11-16-2012 10:37

Quote:

Originally Posted by bmoore (Post 19637715)
Plank- can you give me some quick education on this. Do you think this is SBR specific? Or do you think it would have given way in any rifle? I am not to familiar with SBR.

My money is on the front screw being over-torqued from the beginning, and the damaged thread just gave way over time. I doubt it had anything to do with it being in an SBR.

Quote:

Originally Posted by Travclem (Post 19637747)
I have a factory 10.5" LMT. It has a semi auto carrier and a carbine buffer and is gassed to run in this configuration as per LMT. They say you might have issues with M16 bolt carriers and H/H2 buffers in their SBR uppers.


Until the screw came loose, mine ran like a champ with an H2 buffer and FA BCG.

Edit to add: Got an email back from BCM this morning with some additional questions. They wanted to know what kind of upper I was using, and what kind of ammo I had used. Waiting for a response now after I sent them the info they needed.

Travclem 11-16-2012 10:44

Interesting.

bmoore 11-16-2012 10:46

Copy that

WoodenPlank 11-16-2012 11:33

Got another answer from BCM. They are providing a UPS pre-paid label to return the entire BCG for inspection. It'll be going out to them via UPS tomorrow. Assuming they agree that it was defective from the beginning, and the rest of their turn-around time is as fast as their emails, I get the feeling I will be pleased with their response.

Now I guess it is just a waiting game.


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