Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Did BCM make a mistake on my rail?

  1. #1
    Join Date
    Oct 2009
    Posts
    6
    Feedback Score
    0

    Did BCM make a mistake on my rail?

    Clickbait title aside I do have a question regarding my beautiful new MCMR.15 rail. The picatinny location markings on my rail start at T14 which on any upper I own would cause a double T14 situation. My Midwest rail starts at T16 and I would think that is the correct standard, thoughts?

    Updated note: The rifle is not assembled, so the gap is not a reflection of the rail or upper fit, I simply put them together for an illustration.
    New BCM rail:
    IMG_0143.jpg
    IMG_0144.jpg

    Midwest for comparison:
    IMG_0145.jpg
    Last edited by Colorado S14; 03-24-18 at 21:06.

  2. #2
    Join Date
    Jan 2008
    Location
    AZ-Waging jihad against crappy AR's.
    Posts
    24,902
    Feedback Score
    104 (100%)
    You could try contacting them and asking.



    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

  3. #3
    Join Date
    Oct 2014
    Location
    Northern Virginia
    Posts
    732
    Feedback Score
    10 (100%)
    For what its worth the picatinny on my colt upper receiver sits ever so lightly higher than the MI rail that it came with. It’s the Colt “Combat Unit Carbine”. Not sure who shit the bed on the that but it doesn't effect anything just annyoys me from an aesthetic point of view.

    As far as the T Markings thats your uppers fault. Most receiver markings stop at “T 12”, have a blank slot, then have a small section w/ no slot. Just like the Spikes you posted. The receiver you posted with the BCM rail doesn’t have that “blank” slot and is numbered to “T 14”, so it appears your upper receiver is not mil-spec and is the culprit. Which also wouldn’t surprise me if the height issue was as a result of the upper receiver as well.
    Last edited by sidewaysil80; 03-24-18 at 08:22.

  4. #4
    Join Date
    Oct 2012
    Posts
    4,275
    Feedback Score
    10 (92%)
    Quote Originally Posted by Colorado S14 View Post
    Clickbait title aside I do have a question regarding my beautiful new MCMR.15 rail. The picatinny location markings on my rail start at T14 which on any upper I own would cause a double T14 situation. My Midwest rail starts at T16 and I would think that is the correct standard, thoughts?
    Is the difference in height between the receiver and rail as pronounced as it looks in picture #2?

  5. #5
    Join Date
    Feb 2011
    Posts
    546
    Feedback Score
    0
    All of my rifles (all different brand rails) sit slightly lower than the rail on the receiver. Before the rail is tightened down they're level, but when you start tightening the rail deforms slightly. Doesn't bother me at all.

  6. #6
    Join Date
    Oct 2012
    Posts
    4,275
    Feedback Score
    10 (92%)
    Quote Originally Posted by jackblack73 View Post
    All of my rifles (all different brand rails) sit slightly lower than the rail on the receiver. Before the rail is tightened down they're level, but when you start tightening the rail deforms slightly. Doesn't bother me at all.
    Are any of your rails BCM? Traditional rails with bottom clamp screws deform. BCM rails that clamp at the top do not. That is the beauty of their system.. The nut doesn't have to be timed and the rail doesn't deform.

  7. #7
    Join Date
    Oct 2012
    Posts
    4,275
    Feedback Score
    10 (92%)
    I keep forgetting to answer the OP's question.. The forward most mark on a BCM receiver is T13.

  8. #8
    Join Date
    Oct 2012
    Posts
    4,275
    Feedback Score
    10 (92%)
    I keep forgetting to answer the OP's question.. The forward most mark on a BCM receiver is T12 making the last slot T13.
    Last edited by GH41; 03-24-18 at 18:16.

  9. #9
    Join Date
    Dec 2012
    Location
    TN
    Posts
    799
    Feedback Score
    19 (100%)
    As others have pointed out, it looks like the issue is with the upper and not the rail. At a glance it doesn’t look like a BCM upper. Who makes it?


    Sent from my iPhone using Tapatalk

  10. #10
    Join Date
    Dec 2008
    Location
    Decatur, IN
    Posts
    1,854
    Feedback Score
    89 (97%)
    Quote Originally Posted by Nightstalker865 View Post
    As others have pointed out, it looks like the issue is with the upper and not the rail. At a glance it doesn’t look like a BCM upper. Who makes it?




    Sent from my iPhone using Tapatalk


    Agreed, looking at the picture in question, the upper is NOT a BCM upper. I don't even know what brand upper it is as I've never seen relief cuts down the center length wise on any known QUALITY manufacturers upper receiver.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •