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Sanity-check me on an AR upper build idea?

Discussion in 'Rifle Discussion' started by Diamondback, Sep 22, 2015.

  1. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    I've been starting to think about building an AR upper around some of my own peculiarities and quirks for home-defense, so I thought I'd throw the concept out for discussion and see what potential pitfalls you guys see.

    General note: I like my weapons more muzzle-heavy than normal, it may cost a little more weight but helps with recoil.

    Two questions before starting:
    1. Is there a problem with having a forearm extend past the muzzle and around the flash-suppressor?
    2. Are rifle-length gas systems not used on 14.5" and 16" barrels because of gas pressures, or because the rifle-length gas port is too close to or past those muzzles?

    Concept starts with a 14.5" barrel and a permanently-pinned flash-hider to bring total barrel to at least 16.01", with the longest gas-system that will fit. Whether monolithic-upper or flattop-plus-quad, top rail as close to either the muzzle or the end of the flash-hider as possible--I want every last possible millimeter of sight radius I can get out of the upper's length, while keeping it barely above legal limit.

    We're talking a home-defense instrument for Bad Breath Ranges in an NFA-hostile area, and quarters are so tight that a person above about 300-325# completely fills the entire hallway, and in some places even has to turn sideways to get through, so the goal is something very maneuverable and quick into action.
     
  2. ZA_Survivalist

    ZA_Survivalist Oregon AK's all day.

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    Why not go with a dissipator set up?
    You have all three gas lengths to choose from (from what Ive seen)

    The most reliable being the midlength (from what Ive read)

    Makes your rifle front heavy, gives you a long sight radius.
     
    Medic! likes this.
  3. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    Good point--had never heard of that one before, and the concept appears similar to what I was thinking--though they say many consider it obsoleted by holosights and other optics, part of my thinking was to have a permanent co-witness setup ready to go in case of optic failure, and to start familiarization and training on the range while working on budgeting the optics. (As a freelancer who also has to contribute to supporting two aging relatives, my budget's a bit tighter than most of us.)

    I see why the Mid length came about from the Gunception page on 'em, and also now have a better understanding of gas system lengths from same. :)
     
  4. 9by19

    9by19 New Member

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    The AR in .223/5.56 doesn't have much recoil to start with, so I wouldn't limit yourself by making the rifle too muzzle heavy. For close in distances, you can't beat the size of an AR pistol (just don't shoulder it :)) . The muzzle blast of a short barrelled .223 indoors isn't pleasant, so maybe you want to consider an AR pistol in 9mm.
     
    B5Ben likes this.
  5. Stomper

    Stomper Oceania Rising White Is The New Brown Silver Supporter

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    Also consider that a gas port too close to the muzzle won't give you much dwell-time to push enough gas back through the tube to actuate the bolt properly/consistently.

    IMHO an AR with a carbine length gas-tube loses dependability if the barrel is shorter than 10"-10.5", my preference is 11.5" for an AR SBR.

    As suggested, perhaps consider an AR pistol with a pistol length gas-tube system and learn to hip-fire it since the conditions you mentioned are so tight.

    If you want a rifle, then get a 14.5" barrel with a permanently attached extended flash-hider with a mid-length gas system and low-pro gas-block. I wouldn't run the hand guard over the muzzle device, unless you want a "flaming pig" effect. It'll also heat up that hand guard real quick as the gasses are dissipated out the sides of the cage. Maybe permanently attach a "flaming pig" then run your hand guard up to almost flush with it...
     
    Last edited: Sep 26, 2015
    No_Regerts likes this.
  6. rick benjamin

    rick benjamin USA, Or, Damascus Secure the drama Silver Supporter 2016 Volunteer

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  7. Dyjital

    Dyjital Albany, Ore Flavorite Member Bronze Supporter

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    You can get a faux dissipator setup (Palmetto sells them complete at like $299), they use the tried and true midlength gas system and have the forward sights like you want.

    THere are excellent suggestions above as well.
     
    ZA_Survivalist and No_Regerts like this.
  8. No_Regerts

    No_Regerts United States Well-Known Member

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    With hallways as narrow as you describe it would be easier to use a handgun, barring access to something like an MP5. You can maneuver and pie corners easier with a pistol. You can also suck it in to your body more as you move.

    If a rifle/carbine is what you have to have, I would ease up on the sight radius and weight forward requirement a little bit. Handling characteristics will trump recoil reduction at those ranges.
     
  9. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    For exact numbers, wall-to-wall main hallway is 36", largely reduced to 18-24" up to about 2-3' above floor with various boxes and totes. I'm fairly agile for my bulk (I'm only about 200-and-change, admittedly a little more "and change" than I'd like to admit to but still relatively the "lean and mean" member of the family) so I think I could handle something like a 16" AR or an M1 Carbine (prefer the latter, but former has lower cost and more ready availability on mags and ammo). As it is, current "main battery" is an M1911A1.

    Bullpups do offer reduced length, but there is also the problem of generally being Southpaw Hostile (though the Tavor is an exception; yes, Virginia, there ARE left-handed shooters :p ) and limited supply-chain on spare parts.
     
  10. No_Regerts

    No_Regerts United States Well-Known Member

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    I dont know what kind of reliability they are experiencing, but there is a company making M1 carbine style rifles chambered in pistol cartridges.
     
  11. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    Think Chiappa has a 9mm M1, and I've seen a few in .22LR.
     
  12. B5Ben

    B5Ben Boise Well-Known Member

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    If it's home defense, why not a shotgun?
     
    Last edited: Sep 26, 2015
  13. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    Last time I tried a 12-gauge, it was nowhere near the "fit" I need for something I'd put my life and those of my relatives behind--wrecked my shoulder for a couple weeks and couldn't get sufficient accuracy. I'd seen others get very good accuracy out of that exact same 870 not 5 minutes earlier popping clay pigeons, so I know it was not a "system" issue but a "system/operator mismatch" one.

    If we're looking at downgrading from carbine to pistol, as noted I already carry a 5" Government Model that's never far from reach while sleeping. :)
     
  14. Diamondback

    Diamondback A cold, wet green Hell Well-Known Member

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    TonR, thanks for helping out with the technical "whys and why nots"--that's the kind of info I was looking for. :) So anything from 14.5 up 10 18 is Mid, 18+ is Rifle. Good point re length... Noveske Flaming Pigs are a bit expensive to replace when perma-pinned, not to mention that being a shank to the gut on the warranty. (And I'm still unsure about the FP... the side-views of firing on YouTube make 'em look like mini-flamethrowers.)

    Flash suppressors will be an important thing--I see very well in low-light conditions (as mentioned in other threads, my eyes are so light sensitive I need polarized lenses under most normal lighting conditions), so the more effective at keeping from fricasseeing my own eyeballs the better.

    Sights, I was thinking Aimpoint or similar, but... well, bear in mind I'm also a rifle rookie and it's important to me to learn how to use proper iron sights, in addition to having them available as a backup just in case that POS Murphy is the Dirtbag Home Invader's pointman and buggers the optic. "Have a plan, have a backup plan, and have a backup to the backup" kind of thinking, sort of like how in addition to the reload mags I keep on my person, I carry a spare mag for each primary, and an additional loaded spare for each in my gear-bag.
     
  15. fredball

    fredball Vancouver, WA Well-Known Member

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    Ditto dissipator set up?
     
  16. Garg

    Garg east of portland metro Hold my beer..... watch this Bronze Supporter

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    If I were asked to build this, I would use a 16" HBAR, 5.56, or .223 Wylde, a 15" free float slim handguard, flip up sights, and a 1/3 co-witness red/green something or other.
    Mid length gasser. Full auto BCG in Nib. Pretty much generic everything else.

    But I totally agree with Stomper, a 11.5" pistol configuration is a great HD, and mid range tack driver, IMO. Loud as hell though LOL...
     
  17. clearconscience

    clearconscience Vancouver, WA Well-Known Member

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    If your in a house I'm pretty sure getting a long sight radius is useless.
    Better off putting a laser on it.
    And if your shooting an AR or AR pistol in a confined space you'll probably blow your eardrums.
    Def need a linear comp. you can get cheaper ones that act as well as the more expensive parts.

    If your clearing tight spaces, pistol or AR pistol would be better. If your clearing with pie spacing having a long barrel is going to be a danger to you.

    I have a Miculek comp on my carbine and shooting that outdoors without ear protection ended real quick. That hurt.
    I can't imagine doing that with a pistol and in a confined space.
     
  18. Lance Jacobs

    Lance Jacobs South Willamette Valley Oregon Well-Known Member

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    I think that Stomper is onto something with the AR Pistol recommendation.

    .