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Thread: Installing AR15 Front Site Gas Block, as Just Fixed Front Site? Separate from GB?

  1. #1

    Installing AR15 Front Site Gas Block, as Just Fixed Front Site? Separate from GB?

    Is it possible to install an AR15 fixed front site block forward of where the actual gas block port is, for purposes of just using it as a fixed front site?

    I don't understand how the pins and such secure the FSB to the barrel, so I'm not sure if it actually requires a female cut in the barrel where the gas port is, in order to be secured.

    Or if I could (have a gunsmith) have a low profile as block installed under a handguard rail system, and then separately, install an front site block to the barrel forward of the handguard rail?

    The purpose is to have a more secure front site than attaching a fixed front site to the pic rail of the handguard rail. Whether or not I need a more secure front site than a pic rail attachment is my personal preference, and I like the look better of the FSB set up. Just wondering if it's possible to attach one this way (assuming I have the correct FSB for the barrel outer diameter), or if the attachment will either fail, or be less secure, if it's not done over where the gas block cuts are on the barrel.

  2. #2
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    Quote Originally Posted by Sanch View Post
    Is it possible to install an AR15 fixed front site block forward of where the actual gas block port is, for purposes of just using it as a fixed front site?

    I don't understand how the pins and such secure the FSB to the barrel, so I'm not sure if it actually requires a female cut in the barrel where the gas port is, in order to be secured.

    Or if I could (have a gunsmith) have a low profile as block installed under a handguard rail system, and then separately, install an front site block to the barrel forward of the handguard rail?

    The purpose is to have a more secure front site than attaching a fixed front site to the pic rail of the handguard rail. Whether or not I need a more secure front site than a pic rail attachment is my personal preference, and I like the look better of the FSB set up. Just wondering if it's possible to attach one this way (assuming I have the correct FSB for the barrel outer diameter), or if the attachment will either fail, or be less secure, if it's not done over where the gas block cuts are on the barrel.
    It’s possible.

    Look up KINO and dissipator uppers.

    It’’s ridiculous, and unnecessary but possible.

  3. #3
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    Yes it is. They are most typically secured with taper pins that pass through the outside diameter of the barrel (if I articulated that correctly). There may be some fixed front sights on the market using set screws but I'm not familiar with them off the top of my head.

    At one time there was a configuration referred to as a Dissapator which featured a low profile carbine length gas system concealed under a set of otherwise standard handguards and then a fixed front sight out ahead.

    I never understood the point of that configuration.

  4. #4
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    Quote Originally Posted by rd62 View Post
    Yes it is. They are most typically secured with taper pins that pass through the outside diameter of the barrel (if I articulated that correctly). There may be some fixed front sights on the market using set screws but I'm not familiar with them off the top of my head.

    At one time there was a configuration referred to as a Dissapator which featured a low profile carbine length gas system concealed under a set of otherwise standard handguards and then a fixed front sight out ahead.

    I never understood the point of that configuration.
    The original point of that configuration was to give longer sight radius while maintaining optimal dwell time in 16” barrels.

    There was a certain logic to it before optics became the standard for sighting and before things like mid length gas systems and A5 buffer systems were a thing.

    Now a days - it’s pointless.

  5. #5
    Thanks for the replies. How does the smith/armorer keep the front sight even on the round barrel? I assume it’s easy to install it a little off to the side. Unless I guess you have a jig that holds the upper receiver in place and has a perfectly square aligned groove in the jig for the front sight to be secured?

  6. #6
    Gucci Gear, Walmart Skill Darth_Uno's Avatar
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    As said, look up the BCM Kino.

    Lo and beer hold, JP makes a clamp on A2 sight. https://www.opticsplanet.com/jp-ente...-on-sight.html

  7. #7
    Site Supporter LOKNLOD's Avatar
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    Remember that most barrels are a little smaller in front of the gas block mounting surface, some are tapered.

    The clamp on block, perhaps with some shim material, is probably your best bet. You might be able to dimple and set screw to improve stability. It's easier to swap barrels that pin a new block, unless you're already set up for doing that kind of work.
    --Josh

  8. #8
    Site Supporter rob_s's Avatar
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    Quote Originally Posted by LOKNLOD View Post
    Remember that most barrels are a little smaller in front of the gas block mounting surface, some are tapered.
    This is what I was going to say as well. Adding one after the fact is more challenging and carries more issues than are worth it, IMO.

    I shot a BCM prototype midlength “dissipator” for a year (midlength gas system, front sight mounted at rifle location, 16” barrel) when I went back to irons for awhile. If you want irons, and if you insist on not using a free-float handguard, it *might* be a good option. I don’t think that design ever made it to production so maybe that goes to show how few people actually want it, which in turn I’d call a “clue”.
    Does the above offend? If you have paid to be here, you can click here to put it in context.

  9. #9
    Is it possible? Yes. You will have to get the drilling fixture, a front sight base with an inside diameter to match the barrel, and a barrel with the right diameter near the muzzle. I think finding a barrel with the proper diameter will be the hardest part. You could have a gunsmith turn down a barrel so it would take a .625 FSB.


    https://brdengineering.com/products/...sight-base-jig

    https://bravocompanyusa.com/front-si...at-top-uppers/

  10. #10
    Site Supporter LOKNLOD's Avatar
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    Quote Originally Posted by rob_s View Post
    This is what I was going to say as well. Adding one after the fact is more challenging and carries more issues than are worth it, IMO.

    I shot a BCM prototype midlength “dissipator” for a year (midlength gas system, front sight mounted at rifle location, 16” barrel) when I went back to irons for awhile. If you want irons, and if you insist on not using a free-float handguard, it *might* be a good option. I don’t think that design ever made it to production so maybe that goes to show how few people actually want it, which in turn I’d call a “clue”.
    I like the dissipator format, and I remember wanting that one you had. I still have one in a similar set up as a fun to shoot KISS (is that still a thing?) irons only carbine. But in a world of cheap rigid modular mlok free float systems, it’s pretty much a novelty.

    But more power to anyone making them as I do still think they’re cool
    --Josh

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