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Thread: If you had only two 5.56 AR's? If you had only three? (what Barrel length)

  1. #71
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    Quote Originally Posted by MistWolf View Post
    In one test, M855 ammo made 3000 fps in a 20 inch barrel. Velocity in an 18 barrel was 2900 fps. In the 16 inch barrel velocity was 2800. This is fairly typical. Often, the loss in velocity is greater between 18 & 20 than between 18 & 16, depending on ammo type.


    If the thinking is, why not trade 100 fps to reduce barrel length from 18 to 20 for a slightly handier rifle, why not just trade another 100 fps to cut the barrel back to 16 inches and get a truly handy rifle? A 16 inch will do anything an 18 inch barrel will.

    But what if you want more velocity than a 16 inch barrel? 18 inches only gets you 100 fps, isn't as handy and the 16 inches will still do anything 18 will. If you're going to trade handiness for velocity, might as well go 20 inches for a velocity gain that worth it. The 18 inch barrel also gives you the complication of gas port location. If equipped with a midlength system, blow down time is longer which can lead to over gassing. Rifle length has a shorter blow down time and the rifle becomes particular about ammo. An intermediate length system could be used but then you need to use a proprietary length gas tube. (Personally, I think the proprietary parts thing gets blown out of proportion.) A rifle length handguard can be run with a 16 inch barrel as well. I plan to cut the FSB of a 16 inch carbine and install a rifle length free float tube.

    It's not that the 18 inch barrel is a bad choice, it's just not as practical. It's a tweener without the handling advantage of the 16 inch or the velocity advantage of the 20 inch and the bad habits of both
    I agree 18" is not practical, I don't own nor do I plan to own an 18" barrel on any gun... I was just sorta playing devil's advocate regarding the rifle length gas system (and theoretical advantage of some higher FPS on an SPR type set up).

  2. #72
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    Quote Originally Posted by PatrioticDisorder View Post
    I agree 18" is not practical, I don't own nor do I plan to own an 18" barrel on any gun... I was just sorta playing devil's advocate regarding the rifle length gas system (and theoretical advantage of some higher FPS on an SPR type set up).
    The difference in an 18" SPR type set up is a lot more than just two additional inches of chrome lined carbine barrel that don't compare to an 18" SS, Wylde chambered SPR type set up , which by the way is quite practical for the uses I need it for. Someone should let NSWC CRANE know an 18" barrel is not practical.
    Last edited by DWood; 06-14-14 at 13:09.
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  3. #73
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    Quote Originally Posted by DWood View Post
    The difference in an 18" SPR type set up is a lot more than just the two additional inches of barrel. My 16" CL BCM middy and 10.5" CL LMT are not something I would compare to my 18" SS, Wylde chambered SPR type set up , which by the way is quite practical fot the uses I need it for. Someone should let CRANE know an 18" barrel is not practical.
    *not practical for me as I never shoot past 300 yards...

  4. #74
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    "for me" certainly changes the context of your statement.
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  5. #75
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    I am down to four AR's. I know have a 10.4" pistol (Hk upper/SanTan Tactical lower). I have a 16" Hk MR556 re-profiled to a SOCOM profile with extra 416 14.5" barrel. A CMMG Quebec-A 16".22lr. Finally my RRA 24" Varmint with Vortex scope. If I had to part with one it would be the .22lr, if I had to part with two, the Pistol would make the chopping block next.
    Last edited by CharlieDeltaJuliet; 06-14-14 at 22:47.

  6. #76
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    I would just like to step in here in defense of the 18". They shoot very softly with rifle length gas and are not really that hard to handle provided you don't have too heavy a barrel contour. If you think the 18" is unweildy then just watch a video of almost any top 3 gun competitor.

    I would say the arguments about being particular on ammo are a bit exaggerated. I also think the velocity argument is a little misguided. It seems like the argument is that velocity of the 18" should be on average, in between the 16" and 20". That is fine and true, but arguing that the velocity gain or loss from either of those is worth it seems kind of arbitrary, especially since you can probably see the same 100 fps variation in barrels of the same length based on rifling and such.


    To answer the original question, I would say:
    10.5"/11.5" and an 18" for two
    10.5"/11.5", 16"/18", and a 20"/24" bull/7.5" diplo-style barrel for three

    If non-nfa then:
    18" and 20"/24" bull
    18", 16", and 20"/24" bull
    Last edited by teutonicpolymer; 06-14-14 at 14:16.

  7. #77
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    Go to is a 14.5" mid-length with microdot and my precision is a 20" rifle length with 1-8x optic.
    Last edited by hawk45; 06-14-14 at 15:59.

  8. #78
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    18" - 16 - 10.5"
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  9. #79
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    Quote Originally Posted by teutonicpolymer View Post
    I would just like to step in here in defense of the 18". They shoot very softly with rifle length gas and are not really that hard to handle provided you don't have too heavy a barrel contour. If you think the 18" is unweildy then just watch a video of almost any top 3 gun competitor
    "Not as handy" is a far cry from "unwieldy". I find a 20 inch isn't as handy as a 16 inch barrel but that doesn't mean I find the 20 inch unwieldy

    I would say the arguments about being particular on ammo are a bit exaggerated. I also think the velocity argument is a little misguided. It seems like the argument is that velocity of the 18" should be on average, in between the 16" and 20". That is fine and true, but arguing that the velocity gain or loss from either of those is worth it seems kind of arbitrary, especially since you can probably see the same 100 fps variation in barrels of the same length based on rifling and such
    That's why I said I take velocity figures as a guideline. The general trend is that the 20 inch gives more of a velocity advantage over the 16 than the 18 inch and the 16 inch is handier. In field use (civilian- I'm not LE or Military) I find the 18 and 16 shoot about the same but the 20 shoots noticeably flatter.

    I know the 3 gun guys prefer the 18 inch barrel but I doubt it's from the velocity advantage over the 16 or it's handiness over the 20. I'm willing to bet it gives the shooter a smoother swing than the 16 without needing as much muscle to move as the 20
    Last edited by MistWolf; 06-14-14 at 17:10.
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  10. #80
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    The two I currently own:

    11.5"



    16"



    A third option would be an 18" SPR upper with an optic in the 2.5-10x range.
    Last edited by Boba Fett v2; 06-14-14 at 17:37.
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