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Thread: How to build an ultralight pack gun?

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    How to build an ultralight pack gun?

    I have this idea for an ultralight backpack AR-15.
    I think I'd base it off a Cav Arms lower (can they still be found?), complete it with a Spikes Tactical enhanced LPK.
    for the upper, I'd use a standard M4 flat-top upper with a carbon fiber float tube, JP low-mass carrier, carbon-fiber wrapped 16" mid-length barrel (or, if funds wouldn't allow that a fluted 16" mid-length barrel) and a Vortex flash suppressor. Magpul MBUS rear sight, standard F-height FSB.

    Any other ideas as to how I could make this lighter?

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    You could lose the fixed FSB and use a Magpul front.

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    Quote Originally Posted by Kfgk14 View Post
    I have this idea for an ultralight backpack AR-15.
    I think I'd base it off a Cav Arms lower (can they still be found?), complete it with a Spikes Tactical enhanced LPK.
    for the upper, I'd use a standard M4 flat-top upper with a carbon fiber float tube, JP low-mass carrier, carbon-fiber wrapped 16" mid-length barrel (or, if funds wouldn't allow that a fluted 16" mid-length barrel) and a Vortex flash suppressor. Magpul MBUS rear sight, standard F-height FSB.

    Any other ideas as to how I could make this lighter?
    Why not just go with a standard lightweight carbine build using a 14.5 pinned or 16" LW upper with a standard lower with adjustable stock. Builds like this should be right around 6lbs and are fully functional rifles using proven parts. Bottom line the CAV arms lower is not well proven and the reliability of using a low-mass carrier is not proven either. Plus building a conventional lightweight will be cheaper.

    I did a build like I described and it weighs in a 5lbs 15oz. You could lose more weight even if you go the SBR route using a lw 11.5" or 10.3" barrel.

    https://www.m4carbine.net/showthread.php?t=73857
    Last edited by crusader377; 08-16-11 at 13:53.

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    @ johnson: after adding a railed fore-end, I don't think that it would be worth the very small amount of weight savings, if it would even save any weight at all.
    @ crusader: I don't like the LW profile barrels. Just don't. As to the standard lowers, you add almost a pound over the weight of a Cavalry Arms lower.
    It's cheaper to send a barrel off to Adco for dimpling or fluting than get a $200 tax stamp and wait multiple months.
    Thanks for the suggestions.
    Last edited by Kfgk14; 08-16-11 at 14:43.

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    You'll choose a plastic lower with a spotty record and a fixed stock to save weight (and I'm not sure it's 1 lb, might need to check on that) but you won't go with an A1 profile barrel?

    I think you're fighting a losing battle. If you have a need for a lightweight rifle you have a need for a lightweight rifle, and the barrel is the best place to start.

    Mine is (or would have been):
    14.5" DD lightweight barrel - carbine gas
    muzzle device of your choosing - pinned
    Baer flattop non-FA upper (or Vltor MUR, no FA)
    Troy TRX Extreme handguard - 9.0 length
    Legacy lower
    CAR stock
    Troy battleax grip

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    Quote Originally Posted by Kfgk14 View Post
    @ johnson: @ crusader: I don't like the LW profile barrels. Just don't. As to the standard lowers, you add almost a pound over the weight of a Cavalry Arms lower.
    I don't think the CAV arms lower weighs a pound less than a standard lower. Also, despite the M16/M4 platform being 50 years old, I have never heard or seen pictures of plastic lowers being used by serious end users, ie Military, LE, or private contractors. I think this is a strong clue that plastic lowers lack the quality and durability of a standard mil-spec lower.

    Another question is what are the advantages of going with a fluted barrel over a standard A1 profile barrel?

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    There's never an excuse for a plastic AR lower. EVER.

    I've carried regular old M4s all over the hills with my pack. Any weight sucks... but I'd rather have a good gun with me than a light gun.
    "You people have too much time on your hands." - scottryan

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    Quote Originally Posted by crusader377 View Post
    I don't think the CAV arms lower weighs a pound less than a standard lower. Also, despite the M16/M4 platform being 50 years old, I have never heard or seen pictures of plastic lowers being used by serious end users, ie Military, LE, or private contractors. I think this is a strong clue that plastic lowers lack the quality and durability of a standard mil-spec lower.

    Another question is what are the advantages of going with a fluted barrel over a standard A1 profile barrel?
    Its a pound less than a standard lower with an A2 buttstock.

    A fluted gov't profile barrel is more rigid than an A1 profile barrel, at least that's my understanding. I really need to look at how much weight I'd save with an A1 barrel. I've never actually used one, I have a hard time trusting something that thin.

    In my research, the Cav Arms lowers seem to hold up well.

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    Quote Originally Posted by Kfgk14 View Post
    @ johnson: after adding a railed fore-end, I don't think that it would be worth the very small amount of weight savings, if it would even save any weight at all.
    If an "ultralight" is what you're wanting, any weight savings would be a plus no matter how small. After all, ounces equals pounds.

    Standard FSB weighs 4.7 ounces

    A gas block like the Centurion Arms weighs 1.2 ounces. Magpul MBUS front weighs 1.2 ounces giving you a weight savings of 2.3 ounces.

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    Quote Originally Posted by johnson View Post
    If an "ultralight" is what you're wanting, any weight savings would be a plus no matter how small. After all, ounces equals pounds.

    Standard FSB weighs 4.7 ounces

    A gas block like the Centurion Arms weighs 1.2 ounces. Magpul MBUS front weighs 1.2 ounces giving you a weight savings of 2.3 ounces.
    I'd have to get a railed handguard to mount the FSB. I was planning on getting a CF float tube, sans rails.

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