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Triangle handguard cap?

Discussion in 'Black Rifle Forum' started by trlcavscout, Jan 23, 2011.

  1. So my BCM middy is the first AR I have had with the triangle cap, I want to order a 2 piece quad rail handguard for it but not sure if I need a round cap? I assume I do but I dont have a set of round handguards to try. When I look at the descriptions it just says round fits only A2 and triangle fits A1/A2 so I am not sure.
  2. mainegunner


    Mar 5, 2005
    If you have to replace your cap with a round cap you will have to remove your front sight. You have to tap out your taper pins from left to right and you probably will have to remove your flashhider also. It would be a good idea to get another crush washer for the flashhider since the one your going to remove is crushed. You should be able to leave the gas tube in the front sight/gas block if your carefull.

  3. zhix


    Jan 31, 2010
    I would think most drop in two piece rails for a mid-length would use a triangular cap since that's what most mid-length guns I have seen use.
    I ordered a YHM mid-length rail and it takes a triangular cap. I am 99% sure that no handguards will accept both types of caps.
  4. WayaX

    WayaX Lifetime Member

    Feb 27, 2007
    This. I have surefire M85 midlength rails and they default to a triangle cap, however, a round cap model is also available.
  5. I know how to do it. I had the A2 front sight off twice already on this rifle when I put a FF rail on, then when I took it off because I didnt like how it fit. It was a carbine rail made to fit a middy.

    I checked the Magpul sight and their MOE will fit round or triangle its says? And I found an older article on M4 that says triangle will fit round or triangle but round only fits round? I will just have to find a round set locally and try, or find specific "triangle" HG's. Thanks.
  6. Flashbang1063


    Nov 30, 2010
    Troy Rails fit the triangular cap....

    Troy 2 piece mid-length rail on a BCM mid-length upper with the triangular cap....


    Since you have a BCM upper, you should have no problems with any rails....heck, I even had UTG rails mounted at first to see if I liked rails before my GF bought me the Troy rail.
    Last edited: Jan 24, 2011
  7. lawman800

    lawman800 Juris Glocktor

    I've seen both triangular and round caps with various FF rail handguards. I don't think it makes too much of a difference. The only time it matters is when you use the factory style handguards that have the front part cut out for either shape.