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Will a 1:7 barreled AR shoot a standard 5.56 55 gr bullet well?

Discussion in 'General Firearms Forum' started by WarEagle32, Jul 4, 2012.

  1. WarEagle32

    WarEagle32

    2,571
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    Mar 15, 2011
    Alabama
    I have a 1:9 M4 that I have shot 55 grain bullets through very well for years. I am seriously thinking of buying another AR thats a top tier M4 which has a 1:7 barrel. I have a ton of 55 grain 5.56 stored up. I know the 1:7 will shoot 62gr green tips well, but does it also do well with 55's because I don't want to have to buy more separate larger ammo anytime soon. Thanks for any info!
     

  2. WoodenPlank

    WoodenPlank Who?

    7,958
    3
    May 15, 2010
    NW Florida
    Some people will swear up and down that they got crap accuracy from 55gr with a 1/7 barrel. I've owned several (16, 14.5 and 10.5) 1/7 barrels that were plenty accurate with 55 grain ball, especially federal in various forms. 2-4 MOA is typical, but I have seen as good as 1MOA. My 10.5 SBR will shoot better groups than I will ever get with my 4MOA Aimpoint with Federal XM193.

    As usual, YMMV etc...

    Sent from the USS Sulaco, while nuking the site from orbit.
     
  3. arclight610

    arclight610

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    Dec 2, 2009
    My 1/7 shoots 55gr just fine. In fact, I use 55gr almost exclusively.
     
  4. Decguns

    Decguns

    1,244
    60
    Dec 29, 2003
    NC
    The 55gr FMJ will shoot fine in a 1-7 twist. Under 300 yds, you'll never notice that it's over-stablized. The faster rifling twist actually increases penetration on hard targets like car bodies and GI helmets just like it does for the SS109.

    The only problem I've ever had with 55gr ammo in a 1-7 is shooting soft points at velocities over 3200 fps. The projo is spinning at 300,000+ RPM, and light skinned varmint projectiles can literally self destruct after leaving the barrel. About 3 feet from the muzzle of my Colt HBAR, I'd see a little black puff ball where the projo blew apart.
     
  5. Zombie Steve

    Zombie Steve Decap Pin Killa

    18,083
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    May 31, 2007
    Old Colorado City
    Good point. I wouldn't go with varmint bullet construction or anything lighter than 50 grain bullets.
     
  6. APERS

    APERS

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    May 29, 2009
    Kansas
    55gr works fine in my 1-7" (BCM),, out to around 200yards or so. Also own a 1-9'' Stag that I loaded alot of 52gr BTHP (Nosler) Match bullets for..which I tried the other day while zeroing BCM at 50 yards. They actually grouped tighter than the 68, 62 & 55 gr bullets! Im starting to believe that quality of bbl in an AR has alot more to do with accuracy than twist rate..?? As a side note, both rifles will group the best with 64gr Win. Power Point bullets. At 50 yards that is.. boat tail bullets with excel at longer ranges as a rule of thumb. 250yds and beyond.
     
  7. WarEagle32

    WarEagle32

    2,571
    52
    Mar 15, 2011
    Alabama

    Interesting because I use TAPs and ballistic tips a lot! However pure copper Barnes TSX's are by far my favorite!
     
  8. SCSU74

    SCSU74 St. Cloud Proud

    2,010
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    Jul 24, 2010
    The Northwoods
    Xm193 works great out of my 6920 1/7 out to 50 yds. It works less great I further out I go. At 100 it hits very low and right. Switching to 62g duty ammo at same distance hit dead on. Ymmv


    Sent from my iPhone... which probably auto-corrected something wrong
     
  9. AustinTx

    AustinTx

    7,160
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    Aug 16, 2006
    Tx
    You have noticed something that most gun owners won't believe. Until you do the actual calculation, most people won't believe the bullet is spinning that fast. My son-in-law found that out with light bullets in a 25-06.
     
  10. Redfire SVT

    Redfire SVT

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    May 28, 2011
    Depends on who you ask! But, IMHO, it will shoot them just fine.
     
  11. AustinTx

    AustinTx

    7,160
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    Aug 16, 2006
    Tx
    Well, I didn't ask you, anyway.
     
  12. Redfire SVT

    Redfire SVT

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    May 28, 2011
    I was referring to the OP, who asked for my reply just as much as he did yours. Thanks!
     
  13. AustinTx

    AustinTx

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    Aug 16, 2006
    Tx
    Please excuse me. I don't know what I'm doing most of the time, anyway. I just come here to have fun and maybe even learn something.
     
  14. Tiro Fijo

    Tiro Fijo

    6,281
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    May 31, 2011

    The rate of twist formula is really for bullet LENGTH and not weight, hence your Barnes SC bullet being longer (copper less dense than lead) should do fine.
     
  15. Haldor

    Haldor Retired EE

    7,911
    969
    Oct 22, 2006
    Central Arizona
    Works great. That is how my Colt AR15-A2 is barreled (1:7) and all I shoot through it is M193 ammo. I am getting 3" groups at 100 yards with this combination.
     
  16. eracer

    eracer Where's my EBT?

    6,711
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    Apr 5, 2011
    Tampa, FL
    I have an 18" 1:7 middy that shoots 1 MOA with 75gr TAP, but only 5 MOA with 55 gr. M193. My 1:9 carbine shoots both M193 and 75 gr. Hornady Match to 1 MOA.

    Point is, different barrels handle different ammo differently.