So I just completed my BCM build

This is a discussion on So I just completed my BCM build within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I don't see an o ring. There is a black piece inside of the spring....

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Thread: So I just completed my BCM build

  1. #16
    Member Array gixx1070's Avatar
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    I don't see an o ring. There is a black piece inside of the spring.

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  3. #17
    RKM
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    My original M&P bolt had the o-ring in it. I just thought that was normal. I use the o-ring in my BCM bolt. I just put it in because it was included. I was later informed it's not needed, but I haven't bothered to take it out because it's functioning perfectly fine.

    If yours doesn't have the o-ring that's normal. The black insert is a good thing.

  4. #18
    VIP Member Array jonconsiglio's Avatar
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    I'm not sure what I read that made me think the o-ring was installed. Since it's not, we need to start somewhere else.

    I run a 14.5" BCM mid length and it cycles every type of ammo reliably regardless of the buffer. It's sluggish with weak ammo and an H3, for example, but still runs reliably.

    I'm currently am running an A5, but will be will likely switch back to a carbine RE and an H buffer.

    Now that the o-ring is ruled out, I'm having a hard time not suspecting the bolt carrier being the culprit since PSA's quality control hasn't been the best.

    When can you get to the range again?
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  5. #19
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    It is some sort of extraction problem (not determined to be a mag problem, as it continues to feed....ya just can't get the previous shell out of the chamber. If it's not the extractor, I'd try a different BCG (from BCM)...
    Magazine <> clip - know the difference

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  6. #20
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    Quote Originally Posted by jonconsiglio View Post
    The o-ring needs to come out. Let's start there. It's only needed when you have violent extraction and really need the extractor to grab the case rim. You want the 5 coil spring and black insert but not the o-ring to start with. Remove the o-ring and choose one mag only to use and we'll start there. .
    Jon, you're absolutely right... I meant to say insert, not O-ring. Glad you caught that.
    Smitty
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  7. #21
    Member Array gixx1070's Avatar
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    I'm in NM, I'm going to be headed out around 10ish to pick up different ammo. Can you recommend a quality ammo to try from a local sportsman's warehouse? I don't know if they carry ar mag's if they do I'll pick one up as well.

  8. #22
    VIP Member Array jonconsiglio's Avatar
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    Quote Originally Posted by gixx1070 View Post
    I'm in NM, I'm going to be headed out around 10ish to pick up different ammo. Can you recommend a quality ammo to try from a local sportsman's warehouse? I don't know if they carry ar mag's if they do I'll pick one up as well.
    Anything 5.56. Look for xm193 or xm855. This is hot ammo and will cycle anything well for the most part. Whatever you get, try to pick up 5.56. You can get some 223 as well to compare but we want to test with 5.56 to see what's going on.

    Do you have Yahoo Messenger on your phone? I can PM you my number also so I can help you out while you're at the range if you'd like.

    I just found out my Dad has lung cancer and it may have spread, so I'm a bit of a mess and need to stay busy right now. Let me know what I can do to help you out.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  9. #23
    VIP Member Array jonconsiglio's Avatar
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    Quote Originally Posted by gasmitty View Post
    Jon, you're absolutely right... I meant to say insert, not O-ring. Glad you caught that.
    Ahh, so it's YOUR fault I was thinking he had the o-ring installed..?! :D

    I've seen that happen a few times, people think they need the o-ring then all of a sudden they have issues, which have never occurred before, and for whatever reason they look for some other source than the o-ring they just installed!
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  10. #24
    Member Array gixx1070's Avatar
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    Thanks for the help Jon, pm me your # and I'll get a hold of you when I get to the range.

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    I'm pretty sure DC is going to have to start paying Jon as our AR 15 Subject Matter Expert.
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  12. #26
    VIP Member Array jonconsiglio's Avatar
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    Quote Originally Posted by atctimmy View Post
    I'm pretty sure DC is going to have to start paying Jon as our AR 15 Subject Matter Expert.
    We'll just say I'll accept charitable donations instead of "payment"!


    :D



    Obviously I'm joking...!
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    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

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  14. #28
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    I've been on the phone with the OP for the past 90 minutes while he was at the range. It looks like it cycles well with 5.56 ammo though it was 856 instead of 855! There's only a couple things it could be at this point and he's getting the parts together to finish it out and get it up to 100%.

    BCM mid length gas ports are matched to H buffers for cyclic rate, so that combo is correct, though he'll still try a carbine buffer. At this point, a few more mags may seal up any areas that are bleeding off the gas like at the gas block, or it may need a new bolt carrier group. Not sure yet. I am leaning towards an issue with the carrier gas key, but I'm afraid I may be swayed into that opinion by PSA's shoddy QC of late. The upper and lower are both BCM. It was locking on empty with m856 but nly ejecting about 4 feet or so.

    Of course, as I do with everybody, I've recommended he register at m4carbine and read, read and read all of the stickies and tech info. Every single guy I know that can run a weapon well can also diagnose and work on that weapon, so I feel being educated on the how's and why's of your personal weapons is a must.

    It's refreshing that he came here seeking help instead of going to the local "armorer" or gunshop salesman - who did happen to tell him his rifle was overlubed. Overlubed... It's unbelieveable what these gun shop clowns think they know.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  15. #29
    VIP Member Array jonconsiglio's Avatar
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    Quote Originally Posted by Ring View Post
    I agree that asking there is always a good choice, but he's already received the only possible answers in this thread. I think m4carbine is a great resource. I'm a senior member there and think highly of the site, but there are enough knowledgable members here that simple problems like this should be pretty easy to sort out.
    Proven combat techniques may not be flashy and may require a bit more physical effort on the part of the shooter. Further, they may not win competition matches, but they will help ensure your survival in a shooting or gunfight on the street. ~Paul Howe

  16. #30
    Member Array gixx1070's Avatar
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    Thanks again Jon, you really are the man!!! Please give me the #'s on that ammo you want me to try. Also I ordered the complete bcg from BCM should be here with the other stuff I ordered by next Friday.

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