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5.56 Pistol-What's the best barrel length.?

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  • 850guns

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    Thanks for all the replies! I will search for 10.5-12.5" barrel.
    At one time I was looking to build a "Colt Commando" clone with a pistol lower.
    I believe they were 11.5" barrels. So I guess they did the research for us...as far as reliability.
    I'm thankful for all you guys experience and feedback.
    If not for you, I would probably have gone down the 7.5" rabbit hole....
    Thank you very much.
    Now what about 7.62x39? (I will start a new thread)
     

    Raven

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    Soooooo . . . . lemme see if I understand. You want the AR bbl "as short as possible" but do not want to sacrifice any velocity ?? Do I understand that right ??
    Even with surpressor,go no shorter than 10.5" bbl. The velocity loss would be HUGE !! --- SAWMAN
    Here ya go
     

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    Rebel_Rider1969

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    What's wrong with 7.5?? And 'Mercia!!!
    KG factory built upper. Changed handguard.
     

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    FrommerStop

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    So, I'm putting together a multi-caliber pistol. I have a factory 300 BO pistol. I have since purchased a CMMG Banshee 300 barrel in 9mm. Looking to get their 22 upper as well. I also want a 5.56 upper. But I don't know what length barrel to get. It will be suppressed. I want as short as possible, Without sacrificing reliability and velocity.

    What length barrel do you recommend and why?
    I do not have a recommendation relative to barrel length. But I do have recommendations as to what you need to determine. What velocity do you need to accomplish is what it is you need the gun's bullets to do. The internet has some data for velocity gain/loss per inch of barrel. The 5.56 to achieve its maximum effect needs a lot of velocity. Figure out how much speed your will require from the loads you intend to use to know what is the right barrel length for you.
    For shorter barrels I prefer the 300 BO and 7.62x39.
     

    850guns

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    Also I have seen these "pigtail" gas tubes for AR pistols. I suppose the longer tube increases dwell time. Any one have input on these?
     

    FrommerStop

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    Also I have seen these "pigtail" gas tubes for AR pistols. I suppose the longer tube increases dwell time. Any one have input on these?
    I normally will stick with stock normal equipment and if it works well enough not fix what is not broken. I have short barrels uppers in x39 and 300 bo and so far with an H2 buffer all is working well.
    My first question is if they are self cleaning in the same way that the straight tubes are.
     

    Dan1612

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    No pigtails. The claim that they “increase dwell time” shows they don’t actually understand dwell time.
    Stay away from gimmicky crap.
     
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    Watchmanstan

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    Even though most agree on a 10.5-11.5” optimum. I’ve found that a 7.5” works best for what I want.
    I wanted a small backpack size truck gun that could generate a large amount of firepower. Accurate to 100yds and easy on the ears. Bear Creek upper, Spikes Lower, Folding Stock & Echo trigger, YHM Phantom Suppressor.
    Avg. 2200fps (Measured) PMS 55gr and quiet enough to be comfortable to shoot. I Love it! It eats anything but goes through a lot of it.
    DCB512E4-F790-4C35-83C1-4C8AFCD83BAE.jpeg
     

    G-rat

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    11.5 Faxon Gunner bbl with the midlength gas port. Super reliable and feels like shooting an A2.
     

    Dan1612

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    By now, hopefully OP has started his 11.5” build.

    In general:
    One thing to keep in mind, a 7.5” barrel will never reach fragmentation (main sounding mechanism of 5.56) velocity using standard (M193) ammunition.
    Range toy, noise maker? Fine.
    Defensive tool? Not for me.
    a3948344b0b577e4da928bf129364838.gif

    If you need something shorter than 10.5, go blackout and use SuperSonics.
    If you’re stuck on sub 10.5” 556, piston is best for reliability, and understand it’s ballistic peculiarities.
     
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    Rebel_Rider1969

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    I shoot brown tips in my 7.5. Best idea? No. Most accurate, no. It makes a mess out of small game. I'm guessing it would make a mess out of any looters as well at close ranges. Have had no issues,, KG factory built upper. But its "explosive" Ymmv.
     

    5lima30ret

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    FWIW, I have a 10.5" + a Lantac Dragon brake on my AR pistol and I am happy with it.
    *edit * I have a zero reliability problems shooting even crappy Tula steel cased 55 gr!

    AK&ARpistols.JPG
     
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    Jdcujo

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    11.5"
    now just to remember the brand, thought i bought through dsg but the muzzle device is different than they show.
     

    Ric-san

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    Even if you just start with the barrel, with a DI system, an 11-12 will give you the most reliability for the shorter length.
    Just go with that and take it from there, tuning accordingly as you go. That length will set you up for success with less headaches.
    Dan... who sells 11-12” uppers...? Looking at PSA, all are mainly 10.5” Thanks.
     
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