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Thread: Barrel installation "botchery"?

  1. #31
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    Quote Originally Posted by pinzgauer View Post
    Unless its grossly out of spec this would not account for your issue.
    Incorrect dimensions are likely, especially considering where it came from. I'm finding this out the hard way, which is actually the best way IMO. Now I have one more experience to go by, even though it is agreeably only one data point of many to consider.

    Quote Originally Posted by discreet View Post
    You really don't need to know who bcm gets there stuff from, as it's illrelivant. The fact is you are getting something from BCM, and thats all you need to worry about. ALL BCM stuff is g2g. If there is an issue with a part or product they sell they will take care of you as well...

    FYI I'd just get a blem upper...
    Thanks for your reassurance and recommendation.

    Quote Originally Posted by discreet View Post
    What are you talking about?

    First... BCM IS one of the TOP brands. Second, what does a blem upper have anything to do with his issues? Blem uppers from BCM are 100% in spec. The "blem" ordeal has 0 to do with anything functional or accuracy. There is nothing your DD upper would do that a blem BCM upper wouldn't do. I just mentioned Blem uppers were available and 40$ cheaper than non blem. Please do some research, especially on BCM blem uppers before you hint at the fact they are inferior, as well as hinting at the fact BCM is not 100% top notch from a quality and qc aspect.

    So much overthinking being done here. All this microscopic truing, syncing things up on a mollecular level etc. My god the bench shooter state of mind is mind boggling.
    I didn't get the impression he was hinting at any level of inferiority toward the blemished uppers offered by BCM. I read that only as an empathic statement, and I think that's as far as it was meant. When the dollars come hard and spend easy, it's easy to relate to somebody else getting burned by flashy marketing and poor product delivery.

    Of course, time will tell the difference poor product delivery on their part (not BCM; I mean the suspect upper receiver's brand here) and hideous wrenching on my part. I've learned much more than expected from building this carbine and wouldn't do it differently if I had the choice. Experience complements education.

  2. #32
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    Quote Originally Posted by pinzgauer View Post
    I get it, you love BCM. I hope you got a hat.

    BCM makes fine stuff, no argument.

    You missed my point:

    1) he's chasing ghosts, and has already spent hundreds swapping stuff. Its false economy to save $20 on a blem upper at this point. I'm sure the BCM blem is just cosmetic and should be fine, but in this case its not worth saving $20.

    2) he has a DD barrel. With 1st quality DD uppers available $100-120 assembled, there would be some advantage in matching the barrel to the upper mfg if there's was an issue. ( not that I think his Upper is the problem)

    3) this is not a bench rest issue. Right now DD sub assemblies are a very good value. (Lpk, upper, bcg, etc)

    And I'd put their quality up against anyone's. Not saying they are better, just that they are tier 1 quality currently available at a very good price.


    Sent from my PRC-104 using phonetics
    That was my point in also mentioning a way to save money. There is no "tier 1" stuff. This isn't call of duty lol.

    I do like BCM because of their qc and reputation, plus their excellent cs. Do I have other brands of stuff, yes, including DD and Noveske. They are all right up there quality wise.

    Matching brand of barrel to upper means 0. I have a DD barrel in a BCM upper and is flawless. If itqs in spec it's in spec. Not sure what brand matching has anything to do with it other than OCD.

    IMO a BCM blem is just as "tier one quality" as a DD. May just have a scratch etc here or there, which one hard day at the range will quickly make any mint receiver look 10x's as bad.

    IMO as long as he gets any reputable brand it shouldn't matter who it was from, or if it was blem or not.

    But anyways gone enough off topic with this.

    Let us know if the muzzle device removal has any major impact.
    From TOS ... "buy the shit out of that thing, all the mil spec is just nonsense."

  3. #33
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    I believe the muzzle device is not at fault. Took it out a few hours ago. Shot some, marked the groups shot with muzzle device and ammo type. Removed muzzle device, shot some more, marked the groups without muzzle device and ammo type.

    Groups circled in red were shot without the muzzle device. Groups circled in thin black were shot with the muzzle device attached.

    Vertical distance from the most obvious POA for each group can be explained by me shifting the holdover for off-topic reasons. Please ignore the variations in vertical distance of each group from what the most obvious point of aim should be.

    100_4060.jpg

  4. #34
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    Your groups are stringing. They are not round. If this isn't due to some error on the part of the shooter, this indicates some kind of mechanical shift, either from the bedding or the sight.

    Yes, an AR can have a shift in it's bedding. The AR is bedded where the barrel extension fits inside the upper reciever. If the barrel extension shifts around in there, it will cause a shift in the POI.

    It could also be the sights. The mount or rings could be a poor fit or loose. There could be an internal problem.

    In this case, my gut says it's the bedding, that the barrel extension to upper receiver fit is loose. Some guys will use some kind of epoxy to take any slop (real or imagined) out of the fit. I think this is a bad idea as it will complicate removal at a future date and epoxy tends to break down from shock, vibration, heat & exposure to chemicals. Some will use a facing tool to square the upper. This will remove the anodizing. Aluminum is self healing, that is, with exposure to oxegen, the surface will convert to aluminum oxide but it will not be as deep or as even as the aluminum oxide surface from anodizing.

    I would carefully inspect and tighten the sights, mounts & rings as applicable (check the easiest part first), then remove the barrel nut to check the fit of the barrel extension in the upper. Leave the muzzle device off until you isolate your problem and keep the muzzle threads ptotected. When you do get to re-installing it, do so with minimum torque. Over torquing the MD will distort the barrel and impair accuracy
    Last edited by MistWolf; 01-20-14 at 10:42.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

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  5. #35
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    The name of the manufacturer is irrelevant and BCM doesn't list them for a good reason. But, I can tell you that once they are received in house, they do check them. Anything found out of spec is sent back.

    People assembling AR's need to remember that many uppers and lowers are only made by a handful or companies. BCM is not going to disclose that they buy them from xxxx for a good reason.

    Quote Originally Posted by JRB845 View Post
    Meanwhile, if it does happen to come down to replacing the upper, would this upper from BCM be a decent choice? While BCM is a trusted vendor, the name of the manufacturer of this upper is not mentioned for reputation checks. No offense to BCM here; please understand.
    I have used several of those uppers from BCM with no issues. Good quality for a build. Not sure, but I believe they are the same as used on BCM builds but are not marked with the BCM logo due to being sold as a part only and not a complete upper.[/QUOTE]



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  6. #36
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    Aside from the issue at hand, shooting 3 rounds serves no purpose. Try shooting 5 or 10 round groups. In order to troubleshoot this, you are going to need to isolate the issue. That means following the advice given here about checking everything from A-Z otherwise you are chasing your tail.

    Quote Originally Posted by KF5MLT View Post
    I believe the muzzle device is not at fault. Took it out a few hours ago. Shot some, marked the groups shot with muzzle device and ammo type. Removed muzzle device, shot some more, marked the groups without muzzle device and ammo type.

    Groups circled in red were shot without the muzzle device. Groups circled in thin black were shot with the muzzle device attached.

    Vertical distance from the most obvious POA for each group can be explained by me shifting the holdover for off-topic reasons. Please ignore the variations in vertical distance of each group from what the most obvious point of aim should be.

    100_4060.jpg



    Owner/Instructor at Semper Paratus Arms

    Facebook: https://www.facebook.com/SemperParatusArms/

    Semper Paratus Arms AR15 Armorer Course http://www.semperparatusarms.com/cou...-registration/

    M4C Misc. Training and Course Announcements- http://www.m4carbine.net/forumdisplay.php?f=141

    Master Armorer/R&D at SIONICS Weapon Systems- http://sionicsweaponsystems.com

  7. #37
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    Quote Originally Posted by MistWolf View Post
    ...In this case, my gut says it's the bedding, that the barrel extension to upper receiver fit is loose...

    I would carefully inspect and tighten the sights, mounts & rings as applicable (check the easiest part first), then remove the barrel nut to check the fit of the barrel extension in the upper...
    Thanks for your detailed analysis. Rest assured epoxy or loc-tite between the barrel extension and receiver is a hard negative

    I took the opportunity to break it down, re-inspecting every pinned and threaded point of interest. Everything was tight except for the fit between the barrel extension and upper receiver, as predicted. They fit together and separate without effort and there is a slight wobble between barrel and receiver with all retaining devices (barrel nut and family) removed.

    Quote Originally Posted by Iraqgunz View Post
    ...But, I can tell you that once they are received in house, they do check them. Anything found out of spec is sent back...
    Perfect. Thank you for confirmation. This is exactly what I was looking for.


    Next step is to replace the upper and take it for another test run without muzzle device.

  8. #38
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    Sounds like the slot that the barrel ext slides into is worn.

  9. #39
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    Hard to understand how it wore, unless the barrel was removed and replaced frequently. Sounds like tolerance stacking. Hopefully replacing the upper receiver will eliminate looseness between the barrel extension and upper receiver. If the looseness persists, other than replacing the barrel/extension assembly, an option is to use something like loctite 609. Not a permanent mating like epoxy, but will need to be heated up with a propane torch to disassemble. This method is not unheard of. Believe Alexander Arms uses a loctite product in assembling uppers.

    Edited to change loctite 620 to 609, a lower temp product
    Last edited by mpom; 01-20-14 at 21:45.

  10. #40
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    Quote Originally Posted by mpom View Post
    Hard to understand how it wore, unless the barrel was removed and replaced frequently. Sounds like tolerance stacking. Hopefully replacing the upper receiver will eliminate looseness between the barrel extension and upper receiver. If the looseness persists, other than replacing the barrel/extension assembly, an option is to use something like loctite 690, which is designed to fill in gaps up to .015". Not a permanent mating like epoxy, but will need to be heated up with a propane torch to disassemble. This method is not unheard of. Believe Alexander Arms uses a loctite product in assembling uppers.
    I probably miss read it, but that's the first time I ever heard of Loctite, how does it work?

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