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Disappointed with my AR w/55 grain bullets

Discussion in 'Ammunition & Reloading' started by dirtyd, Mar 21, 2014.

  1. dirtyd

    dirtyd Kenmore Active Member

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    So I have a Colt AR that started as a standard LE6920 (16" w/ 1 in 7" twist rate) and since then I free floated the barrel and did some other minor changes as well as a 4-12x p-223 scope. My plans for the rifle were to be a decent bench and coyote gun.

    I played around with some 50 & 55 grain factory loads as well as some hand loaded 55 grain rounds loaded down to around 2800fps due to the higher twist rate. Anyways, I'm really disappointed with my accuracy out of the gun, I feel pretty lucky if I get 1 MOA out of the thing. I've been shooting since I was about 5 and can almost put them through the same hole with my .17 or .308 so I dont think my user error is all that bad.

    With the tight twist I was thinking of trying some 69 grain Sierra Match Kings or Berger's. Anyone have any advice or think a heavier bullet may help?
     
  2. jluck

    jluck Really,Really, Close to Newport Oregon 97365 Voted #1 Member

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    A heavy (long) bullet is needed.
     
  3. Classic

    Classic Federal Way WA Well-Known Member

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    A 1 in 7 requires heavy bullets for accuracy. 69 gr aint bad buy if you're going to spend the money for 69's ya might as well get the 77 gr which come to life in a 1 in 7 barrel... Just saying ;)
     
    JVK and My 3 sons like this.
  4. Certaindeaf

    Certaindeaf SE Portland Well-Known Member

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    I always liked the 55 grain ball for the way they macerate flesh.
     
  5. Certaindeaf

    Certaindeaf SE Portland Well-Known Member

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    Oh, and were you shooting cheap 55 grain FMJ pills? They aren't noted for their accuracy out of anything.. regardless of the care they are loaded with.
     
  6. Bxc53

    Bxc53 Arlington Wa Member

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    I've had good luck with 55's in a similar barrel with reloads using 21.5 gr of Reloader 7. This is a published load from Sierra. I can get sub MOA for 4-5 shots in a minute, then the POI will shift as the light barrel heats. If you need sustained rapid fire for varmints, etc, you might look at changing to a longer, heavy barrel.
     
  7. Nwcid

    Nwcid Yakima and N of Spokane Well-Known Member

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    I agree, you need heavier bullets. That is why a lot of guns for commercial sales are 1/9 as it performs well with heavier (longer) and lighter (shorter) bullets.
     
  8. SinisterSouthpaw

    SinisterSouthpaw SW WA Active Member

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    The faster you spin the bullet, the more opportunities for any flaw or imbalance has to affect the trajectory. A great many standard grade bullets are flawed and flawed mainly in the jacket. The heavier (longer) bullets will not exhibit the effects of a small flaw as much as a lighter bullet will, given the same flaw. A 55 gr. bullet that is light .2gr on one side will be more affected than a 70gr. bullet with the same flaw. Standard grade hunting/plinking bullets are not held to the same tolerances nor are they constructed the same as the match bullets normally used in bench shooting. There are companies selling match/varmint bullets, too.

    Ideally, we select a barrel twist rate based on the rifle's intended application (therefore the weight and type of bullet will be known) and before the gun is purchased. Unfortunately when we buy off the rack, we take what we can get and end up approaching the subject backwards, as in this case. IMHO premium bullets like Berger, Lapua, and others are pretty much required to get the best out of a fast twist barrel.
     
  9. the4thshake

    the4thshake Portland Active Member

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    All of my 1-7 twist barrels do great with 55 grain bullets. I run them a lot faster than 2800 fps too. They like the heavier bullets as well.
     
  10. jordanka16

    jordanka16 Albany, OR Active Member

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    You need either heavier bullets, or hotter loads. My 1/7 would work just fine with standard 55gr factory ammo, but some light handloads would cause keyholes.
     
  11. BAMCIS

    BAMCIS Eugene Well-Known Member

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    A few weeks ago, shooting factory UMC 55gr, the wife and I were dinging 20" steel at 400 yds with open sights out of my BCM A4 . The only modification (so far) has been free floating the barrel with a Daniel Defense Omega Rail. For those who do not know, all Bravo Company rifles to my knowledge are 1/7.

    IMG_0384001_.jpg
    (pic "borrowed" from BCM)



    (pic "borrowed" from Daniel Defense)​

    Maybe I will post pics later, if anyone wants to see them. But I'm getting ready for bed now. Sorry.
     
  12. vertical ascent

    vertical ascent Vancouver Active Member

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    Its been years since I seen that term BAMCIS, OOOOOORRRRRAAAAAHHHH!!!!!!!
     
  13. Nwcid

    Nwcid Yakima and N of Spokane Well-Known Member

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    Interesting, it does not say on their site. If you look at your barrel, between the front sight and the flash hider it should be stamped with the twist rate. ​
     
  14. BAMCIS

    BAMCIS Eugene Well-Known Member

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    Semper Fi!
     
  15. BAMCIS

    BAMCIS Eugene Well-Known Member

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    You're right they are stamped. Well, at least all three of my BCM's are.

    IMG_8147_zps4bc053c4.jpg

    IMG_8138_zpsa7434651.jpg
    (Actually, the M4 in the upper right is the wife's)

    IMG_8141_zps122a3d4b.jpg

    IMG_8144_zps075f97ed.jpg

    It's a little hard to find, but this is on BCM's web site:

    twistrate_zpsa93564ec.jpg


    http://www.bravocompanyusa.com/AR15-M16-M4-Barrel-Assemblies-s/3.htm

    Click on any of the offered barrels.

    /
     
    Nwcid likes this.
  16. rick benjamin

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

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    DirtyD;
    No baseline, start from scratch.
    I would:
    Verify the barrel and shroud properly tightened to the receiver
    Inspect the muzzle crown for imperfections, fix
    Lap the barrel with CBL-4
    shoot it (Fed XM193) from a firm rest (w iron sites) to set baseline
    Mount the scope, shoot it.
    If there isn't any change, your system is baselined using XM193.

    shoot it (Hornady 75grBTHP) firm rest. H75BTHP baseline

    If you don't use a chronograph, you are only guessing and hoping.
     
  17. rick benjamin

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

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    Old Corps,,,
    S.M.E.A.C
    Semper Fi
     
    BAMCIS likes this.
  18. SinisterSouthpaw

    SinisterSouthpaw SW WA Active Member

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    ad mort


    -super breed of the old breed


    1st of the 1st
    eng/div
     
  19. AMProducts

    AMProducts Maple Valley, WA Jerk, Ammo Manufacturer Silver Supporter

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    So what load were you pushing, what bullets? There's not much we can really poke into to figure out what's wrong. I'm inclined to say the problem is you bought a colt.
     
  20. Ron Eagle Elk

    Ron Eagle Elk Outside Ft Lewis East Gate Active Member

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    I've been shooting 70 grains Berger VLD's out of my BCM upper with a 20 inch barrel and a 1:7 twist. With 24.6 grains of Varget I get 6 shot groups I can cover with a quarter at 100 yards.