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*Update - Key Screw Broken* Failure to Extract/Insufficient Gas Pressure Strange Phenomenon
6/2/2012 8:38:47 PM
So... range trip with the new T1 and Battlecomp. Great stuff, but....
The gun was essentially a bolt action. Never extracted a casing once. I had to charge it every single time, in 210 rounds. Tried brass and steel, ranging from 55grn to 77 grn. 7 weeks ago, it worked totally fine, as shown in the other vids. The only difference is the addition of the Battlecomp.
It looks like there is not enough gas pressure pushing the carrier back. Never pulled far enough to extract, but it did reset the trigger sometimes. Did a bunch of stuff at the range to deal with it, had the range gunsmith look at it. He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
Here's the composition of the upper:
BCM Unmarked Upper
DD 16" middy barrel with pinned GB
BCM BCG + CH
Battlecomp
KAC URX III
I'm assuming the gas block has developed a leak. No idea why. The first video is today, the second one is 7 weeks ago (the last time the rifle was shot)
Compare that to:
Thoughts?
The gun was essentially a bolt action. Never extracted a casing once. I had to charge it every single time, in 210 rounds. Tried brass and steel, ranging from 55grn to 77 grn. 7 weeks ago, it worked totally fine, as shown in the other vids. The only difference is the addition of the Battlecomp.
It looks like there is not enough gas pressure pushing the carrier back. Never pulled far enough to extract, but it did reset the trigger sometimes. Did a bunch of stuff at the range to deal with it, had the range gunsmith look at it. He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
Here's the composition of the upper:
BCM Unmarked Upper
DD 16" middy barrel with pinned GB
BCM BCG + CH
Battlecomp
KAC URX III
I'm assuming the gas block has developed a leak. No idea why. The first video is today, the second one is 7 weeks ago (the last time the rifle was shot)
Compare that to:
Thoughts?
6/2/2012 9:08:14 PM
My only thoughts are that while torquing the battlecomp on you moved something in the gas system.
You didn't do anything to the gas block or tube for any reason?
You didn't do anything to the gas block or tube for any reason?
6/2/2012 9:10:39 PM
I suppose that is possible, haven't considered it. I haven't even touched the gas block.
6/2/2012 9:12:40 PM
The gas block is pinned so I doubt that it moved so it has to be related to the Battlecomp installation.
Did you clamp the barrel to install? If you just had the upper receiver in the vise and applied torque to the barrel the aligning pin can eat into the sides of the notch of the upper and your barrel could rotate taking the gas tube out of alignment.
If that is the case your bolt carrier should not be sliding as well as before as the gas key enters in contact with the gas tube...
Did you clamp the barrel to install? If you just had the upper receiver in the vise and applied torque to the barrel the aligning pin can eat into the sides of the notch of the upper and your barrel could rotate taking the gas tube out of alignment.
If that is the case your bolt carrier should not be sliding as well as before as the gas key enters in contact with the gas tube...
6/2/2012 9:15:15 PM
It is possible to damage an upper by torqueing the crap out of a muzzle device. You would have trouble closing the bolt if you twisted the barrel in the upper receiver. I doubt this is your problem. I would disassemble your bolt and carrier and inspect it for foreign objects or missing parts.
6/2/2012 9:16:05 PM
Originally Posted By erne75:
The gas block is pinned so I doubt that it moved so it has to be related to the Battlecomp installation.
Did you clamp the barrel to install? If you just had the upper receiver in the vise and applied torque to the barrel the aligning pin can eat into the sides of the notch of the upper and your barrel could rotate taking the gas tube out of alignment.
If that is the case your bolt carrier should not be sliding as well as before as the gas key enters in contact with the gas tube...
The gas block is pinned so I doubt that it moved so it has to be related to the Battlecomp installation.
Did you clamp the barrel to install? If you just had the upper receiver in the vise and applied torque to the barrel the aligning pin can eat into the sides of the notch of the upper and your barrel could rotate taking the gas tube out of alignment.
If that is the case your bolt carrier should not be sliding as well as before as the gas key enters in contact with the gas tube...
I used a barrel vise, so it's not that.
This sucks, especially since I can't just function test it in my house.
The gunsmith at the range just said to use a chamber brush. I did as he suggested in the middle of the range trip, but the obviously wasn't the issue. As soon as he said BCM sucked, I knew that he wouldn't give me any good info.
6/2/2012 9:17:08 PM
Originally Posted By borderpatrol:
It is possible to damage an upper by torqueing the crap out of a muzzle device. You would have trouble closing the bolt if you twisted the barrel in the upper receiver. I doubt this is your problem. I would disassemble your bolt and carrier and inspect it for foreign objects or missing parts.
It is possible to damage an upper by torqueing the crap out of a muzzle device. You would have trouble closing the bolt if you twisted the barrel in the upper receiver. I doubt this is your problem. I would disassemble your bolt and carrier and inspect it for foreign objects or missing parts.
I disassembled it completely after the first few rounds at the range. Didn't see anything strange. I even took out the black insert from the extractor, but it didn't make a difference.
6/2/2012 9:18:26 PM
Originally Posted By osha:
I disassembled it completely after the first few rounds at the range. Didn't see anything strange. I even took out the black insert from the extractor, but it didn't make a difference.
Originally Posted By borderpatrol:
It is possible to damage an upper by torqueing the crap out of a muzzle device. You would have trouble closing the bolt if you twisted the barrel in the upper receiver. I doubt this is your problem. I would disassemble your bolt and carrier and inspect it for foreign objects or missing parts.
It is possible to damage an upper by torqueing the crap out of a muzzle device. You would have trouble closing the bolt if you twisted the barrel in the upper receiver. I doubt this is your problem. I would disassemble your bolt and carrier and inspect it for foreign objects or missing parts.
I disassembled it completely after the first few rounds at the range. Didn't see anything strange. I even took out the black insert from the extractor, but it didn't make a difference.
whats odd to me is that you have to mortar it to eject the spent casing
6/2/2012 9:21:26 PM
Yeah, that was with the steel and the chamber was already pretty carboned-up. About half of the time I was able to just charge it normally.
6/2/2012 9:21:59 PM
is the carrier key loose?
6/2/2012 9:25:43 PM
Everything is super tight, the way it looks to me. Carrier key is staked, per BCM standards.. I still haven't taken off the bottom of the URX to look for carbon trails.
6/2/2012 9:44:46 PM
Is this amount of carbon escaping from the GB not normal? You can see some of it in front of the GB.
6/2/2012 9:50:44 PM
I'd guess that you have a clogged gas tube. Were you using Wolf at all?
6/2/2012 9:52:26 PM
Yes, about a hundred of the rounds fired were Wolf. However, I'd used it in the past without any problems...
How would I unclog the gas tube? That definitely sounds like a good lead...
How would I unclog the gas tube? That definitely sounds like a good lead...
6/2/2012 9:56:00 PM
I would check the carrier key. I had a rifle that had worked fine and then all of a sudden was doing the same thig yours was. Checked the carrier key and one of the bolts had broke. Replaced it and now its good to go.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
6/2/2012 10:00:53 PM
Originally Posted By mwoodrow84:
I would check the carrier key. I had a rifle that had worked fine and then all of a sudden was doing the same thig yours was. Checked the carrier key and one of the bolts had broke. Replaced it and now its good to go.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
I would check the carrier key. I had a rifle that had worked fine and then all of a sudden was doing the same thig yours was. Checked the carrier key and one of the bolts had broke. Replaced it and now its good to go.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
Ok, so the front key screw came loose fairly easily, but because it is staked, I can't get it out.
Also, how would I go about fixing this? Do I get another screw and just tighten it, or do I need to re-stake it? I don't think I have the equipment for that.
6/2/2012 10:12:30 PM
Originally Posted By osha:
Ok, so the front key screw came loose fairly easily, but because it is staked, I can' get it out. Also, how would I go about fixing this? Do I get another screw and just tighten it, or do I need to re-stake it? I don't think I have the equipment for that.
Originally Posted By mwoodrow84:
I would check the carrier key. I had a rifle that had worked fine and then all of a sudden was doing the same thig yours was. Checked the carrier key and one of the bolts had broke. Replaced it and now its good to go.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
I would check the carrier key. I had a rifle that had worked fine and then all of a sudden was doing the same thig yours was. Checked the carrier key and one of the bolts had broke. Replaced it and now its good to go.
ETA: You can't tell by just looking at it, grab an allen wrench and put a little torque on the bolt trying to loosen it, if it all of a sudden becomes very easy to turn then its probably broke.
Ok, so the front key screw came loose fairly easily, but because it is staked, I can' get it out. Also, how would I go about fixing this? Do I get another screw and just tighten it, or do I need to re-stake it? I don't think I have the equipment for that.
35 - 40 inch pounds is the torque spec for those.
It's not much and that's why it came loose easily.
Don't monkey with those unless the plan is replacement of the screws and possibly the key.
The screws are a one-time use item.
Here's an easy check to do....
Get a piece of tubing, the clear plastic stuff for instance, of the correct ID that will slip over the gas tube end that is inside the receiver.
Blow on it....you will know in 0.5 sec whether or not it is plugged.
If it's plugged you will have to pull tube and maybe the gas block to clean and re-install.
6/2/2012 10:16:31 PM
So, looks like the screw was snapped in half. Not sure how to get the bottom half out –– it's threaded in.
I guess I should tell BCM.
I guess I should tell BCM.
6/2/2012 10:24:14 PM
I think this is the 3rd BCM carrier key screw Ive read about breaking.
I have all kinds of BCM stuff and am not bad mouthing at all, but hope they have since solved the issue.
When did you buy the BCG?
I have all kinds of BCM stuff and am not bad mouthing at all, but hope they have since solved the issue.
When did you buy the BCG?
6/2/2012 10:25:50 PM
I got the BCG brand new back in December, only have about 350 rounds fired with it.
I posted this in their Industry page, and hopefully will get it fixed soon.
I posted this in their Industry page, and hopefully will get it fixed soon.
6/2/2012 11:10:38 PM
Even proper heat treated grade 8 fasteners can break if it was over tourqued to begin with.
6/2/2012 11:29:31 PM
Originally Posted By Saddlerocker:
I think this is the 3rd BCM carrier key screw Ive read about breaking.
I have all kinds of BCM stuff and am not bad mouthing at all, but hope they have since solved the issue.
When did you buy the BCG?
I think this is the 3rd BCM carrier key screw Ive read about breaking.
I have all kinds of BCM stuff and am not bad mouthing at all, but hope they have since solved the issue.
When did you buy the BCG?
This is the fifth BCM broken gas key bolt I've read about since late December.
6/2/2012 11:35:13 PM
Originally Posted By osha:
He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
Not the first BCM bolt carrier with a busted key screw. The more agressive the staking the more likely a broken screw. The harder the screw the more likely a broken screw upon staking. The tighter the screw the more likely a broken screw upon staking. Proper grade screw with proper torque and adequate staking and you wont get a broken screw. go overboard on the torgue or the staking and you might. go overboard on both and you will.
6/2/2012 11:36:48 PM
Originally Posted By AR15fan:
Not the first BCM bolt carrier with a busted key screw. The more agressive the staking the more likely a broken screw. The harder the screw the more likely a broken screw upon staking. The tighter the screw the more likely a broken screw upon staking. Proper grade screw with proper torque and adequate staking and you wont get a broken screw. go overboard on the torgue or the staking and you might. go overboard on both and you will.
Originally Posted By osha:
He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
He looked at the rollmark on the lower and said "There's your problem right there" –– it's a BCM lower.
Not the first BCM bolt carrier with a busted key screw. The more agressive the staking the more likely a broken screw. The harder the screw the more likely a broken screw upon staking. The tighter the screw the more likely a broken screw upon staking. Proper grade screw with proper torque and adequate staking and you wont get a broken screw. go overboard on the torgue or the staking and you might. go overboard on both and you will.
+1
I agree with this^^^
6/2/2012 11:47:16 PM
Interesting stuff, guys... I'm sure they're going to take care of me, hopefully it won't happen too many more times in other BCGs before they do them all right.
6/2/2012 11:55:04 PM
Parts brake all the time just the higher quality stuff brakes less often, Could be a 100 different reasons why it broke.. call BCM they will fix it. I have about 3k through my BCM upper brass and steel no issue
6/2/2012 11:57:30 PM
Absolutely, I have no doubt that BCM will make it right, and I don't have any reservations about recommending them to a friend. It just sucks that it happened after only 150 rounds (I shot about 200 rounds today after the problem had already occurred).
6/3/2012 3:06:48 AM
Makes you wonder why they don't just make carriers one piece. (really would like to know the purpose of having a replaceable gas key, this is coming from a LWRC piston guy so I wouldn't know)
6/3/2012 4:57:44 AM
Originally Posted By osha:
So, looks like the screw was snapped in half. Not sure how to get the bottom half out –– it's threaded in.
http://i85.photobucket.com/albums/k49/Poopstania/AR15/102_0772.jpg
I guess I should tell BCM.
So, looks like the screw was snapped in half. Not sure how to get the bottom half out –– it's threaded in.
http://i85.photobucket.com/albums/k49/Poopstania/AR15/102_0772.jpg
I guess I should tell BCM.
Well glad you found that that is what it was. As far as getting the bottom piece out, once you take the back bolt out and take the actually key part off then it may just thread right out, all depends on if they have loctite on the screws. If there is then may need to add some heat to it and use a pair of pliers. I wouldn't doubt that BCM would take care of it as I am sure PSA would have taken care of mine but like someone else said, parts break so I would just go ahead and fix it myself as I did with mine when it did break.
6/3/2012 6:05:09 AM
Originally Posted By jds24:
Makes you wonder why they don't just make carriers one piece. (really would like to know the purpose of having a replaceable gas key, this is coming from a LWRC piston guy so I wouldn't know)
Makes you wonder why they don't just make carriers one piece. (really would like to know the purpose of having a replaceable gas key, this is coming from a LWRC piston guy so I wouldn't know)
manufacturing costs
6/3/2012 10:41:36 AM
Originally Posted By apierce918:
manufacturing costs
Originally Posted By jds24:
Makes you wonder why they don't just make carriers one piece. (really would like to know the purpose of having a replaceable gas key, this is coming from a LWRC piston guy so I wouldn't know)
Makes you wonder why they don't just make carriers one piece. (really would like to know the purpose of having a replaceable gas key, this is coming from a LWRC piston guy so I wouldn't know)
manufacturing costs
Ummm wrong.
I guess yall dont know how the DI system works.
Gas from the gas tube enters the gas key and it sfiltered into the bolt carrier behind the bolt.
To make a BCG you have to drill a hole through the bolt carrier for gas to enter, you cant do that with a carrier key on it, drill cant make sharp turns they have to go up and down
You drill the carrier key, drill the bolt carrier then put them together
6/3/2012 10:53:54 AM
Not manufacturing costs but simply manufacturing as Sinless said its the way its built and made that requires 2 seperate pieces besides carrier keys can get damaged and if they could and did make them 1 piece the whole carrier would need to be replaced if the key were damaged.On piston rifles you need a 1 piece but its a hump and not a key to take the abuse of a rod although first generation Osprey 416s had a key replacement so you could modify an existing carrier but then switched to a 1 piece for stregnth and reliability.
6/4/2012 8:58:26 AM
BCM is sending me a shipping label shortly, and will send me a replacement carrier as soon as they receive the defective one.
6/4/2012 9:53:32 AM
Broken steel.....all of these case = poor heat treatment. If steel is heat treated incorrectly for the purpose it is used for.....the results can be devastating.
In heat treatment just a few degees difference and the steel can be to brittle or soft depending.
BTW, i receive this from BCM :
Thank you for contacting us. There are a number of different reasons that a quality part can break as indicated in this picture. Overall, there are no issues with our BCM Bolt Carrier Group. Our BCM products are put through an extensive quality control process. Our BCM BCG is parkerized exterior and chrome lined inside the carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg. Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts insure a strong staking and proper gas system functioning.
The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).
Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. Please feel free to email any other questions you have.
Bravo Company USA, Inc.
In heat treatment just a few degees difference and the steel can be to brittle or soft depending.
BTW, i receive this from BCM :
Thank you for contacting us. There are a number of different reasons that a quality part can break as indicated in this picture. Overall, there are no issues with our BCM Bolt Carrier Group. Our BCM products are put through an extensive quality control process. Our BCM BCG is parkerized exterior and chrome lined inside the carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg. Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts insure a strong staking and proper gas system functioning.
The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).
Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. Please feel free to email any other questions you have.
Bravo Company USA, Inc.
6/4/2012 1:08:13 PM
Originally Posted By MISTERMOON:
Broken steel.....all of these case = poor heat treatment. If steel is heat treated incorrectly for the purpose it is used for.....the results can be devastating.
In heat treatment just a few degees difference and the steel can be to brittle or soft depending.
BTW, i receive this from BCM :
Thank you for contacting us. There are a number of different reasons that a quality part can break as indicated in this picture. Overall, there are no issues with our BCM Bolt Carrier Group. Our BCM products are put through an extensive quality control process. Our BCM BCG is parkerized exterior and chrome lined inside the carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg. Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts insure a strong staking and proper gas system functioning.
The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).
Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. Please feel free to email any other questions you have.
Bravo Company USA, Inc.
Broken steel.....all of these case = poor heat treatment. If steel is heat treated incorrectly for the purpose it is used for.....the results can be devastating.
In heat treatment just a few degees difference and the steel can be to brittle or soft depending.
BTW, i receive this from BCM :
Thank you for contacting us. There are a number of different reasons that a quality part can break as indicated in this picture. Overall, there are no issues with our BCM Bolt Carrier Group. Our BCM products are put through an extensive quality control process. Our BCM BCG is parkerized exterior and chrome lined inside the carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg. Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts insure a strong staking and proper gas system functioning.
The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).
Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. Please feel free to email any other questions you have.
Bravo Company USA, Inc.
Even the best parts can brake... shit happens
6/4/2012 3:19:49 PM
I dont know your exact round count, but you may also want to replace those gas rings. I have been taught to always replace gas rings during a carrier key exchange, especially when/if the rifle ceases to function.
6/5/2012 1:41:55 PM
I think it is fair to say that had this been a PSA or Spikes or similar BCG, many would have come to another conclusion regarding the cause of this break.
6/14/2012 2:48:50 PM
Got my carrier back soon after sending it with a prepaid label they gave me. Everything looks fine, and I will take it to the range and do a Surefire 60 mag dump on video for the sake of making sure it is fixed. 
6/14/2012 3:30:56 PM
