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Bullet weights for 1/7 twist

Discussion in 'Rifle Country' started by 12Pump, Oct 17, 2013.

  1. 12Pump

    12Pump Well-Known Member

    Could someone tell me what they use for bullet weights when you have a 1/7 twist barrel? That's what I have. I googled this subject and found different answers so I don't know which one to go by. First, I heard anything 55 grains and up, and also 62-77 grains, while 1/9 is for 55 grains.

    I'm mostly interested in shooting 55 grains, since that it the cheapest, which isn't cheap at all, but sure beats the price of everything above it.
  2. On An Island

    On An Island Well-Known Member

    What caliber?
  3. ugaarguy

    ugaarguy Moderator Staff Member

    I'm assuming you're asking in regards to .223 Rem / 5.56 NATO cartridges since you just got your first AR-15.

    You can shoot pretty much any .224" bullet weighing 80 grains or less in a 1:7 twist bbl. If you want to shoot really thinly jacketed varmint bullets you'll have to limit the velocity to avoid tearing the jacket.
  4. MtnCreek

    MtnCreek Well-Known Member

    Any bullet weight (you may have issues with 90gr+ bullets, I don't know). For cheap plinkers, I use 55gr Hornady FMJ reloads.

    Shooters Pro Shop has a pretty good deal on Nosler 77gr HPBT seconds right now. After shipping I'm a hair over $0.16 / bullet. Worth checking out if you reload.
  5. 12Pump

    12Pump Well-Known Member

    That info would have been helpful, right? My mind has been so one-tracked lately about AR15's that I forgot there's anything else out there! Caliber is .223.

    Thanks! Sounds like 1/7 twist is pretty universal when it comes to bullet weights. People seem to like 1/7 most. Maybe that's why.
  6. MtnCreek

    MtnCreek Well-Known Member

    That limits your bullet selection, assuming you want them to feed through the mag. Not a complete list at all, but as a general rule 77gr HPBT's are as long a bullet that will feed through the mag. 75gr Hornady A-max will not. Anything shorter will work.
  7. gotigers

    gotigers Well-Known Member

    My 1:7 likes all weights, but 68 through 77 shoot the best. SMK's best, Hornady BTHP then everytbing else. I have not tried Barnes or Nosler.
  8. 556by45guy

    556by45guy Well-Known Member

    I've only shot 55/64/65/77gr (nothing lighter or heavier) out of my 1-7 AR, but it doesn't seem one weight shoots any better than another. My 55gr and 65gr handloads easily do 5 shot sub-MOA at 100m as do my BH 77gr.
  9. Arizona_Mike

    Arizona_Mike Well-Known Member

    Generally overstabalization is much less critical than under. That said, I think the main reason the military standardized 1:7 is because of the very long M856A1 tracer which matches the drop of the 62-gr M855 steel tip. As far as dedicated marksman/sniper weapons in the US inventory the Mk 12 SPR did go with a 1:7 for the Mk262 77gr Sierra Matchking, but the Seal Recon Rifle chose 1:8 as being optimum for the same round, AND the Marine SAM-R uses 1:7.7.

    One thing I've found from playing with the Miller twist formula or the long version of the Greenhill's formula is that air density (from both temperature and altitude) makes a huge difference without going to extremes of either.

    I still think that 1:8 is probably the best civilian twist but you will probably not see major overstabalization effects with 55gr bullets.

    Last edited: Oct 17, 2013
  10. gotigers

    gotigers Well-Known Member

    I didn't think you could over stabilize a bullet.

    The 1:12, 1:14 twist won't stabalize the heavy stuff. 1:9 can be iffy stabalizing over 68 grains. I've never had a keyhole on paper shooting light ammo, <50gr, from my 1:7. they doesn't have good groups, but they bullets stabalize.

    I have 2 1:8 twists as well. They seem to shoot everything well.
  11. MtnCreek

    MtnCreek Well-Known Member

    ^ Good reading below. I'd read where several folks mentioned over-stabilization and couldn't get my head wrapped around it. I found the below and I'm not saying I fully understand it, but I at least accept it. :) Despite the info below, I still think a Hornady 55gr FMJ fired from a 1:whatever twist AR is the best range fodder ever devised. :)

  12. nastynatesfish

    nastynatesfish Well-Known Member

    Mine will shoot 55gr so in about a 12" group. It does like the 68-69. Haven't tried any heavier though
  13. joed

    joed Well-Known Member

    I've owned 2 rifles chambered in .223, one had 1:9" twist, the other 1:7" twist. Both did not like anything under 55 gr. The 55 gr bullet shot mediocre in my opinion and the 69 gr and up were very good.

    Lots of people say they have not experienced the above with fast twist. I have and will only shoot the 69 gr or heavier stuff.
  14. itsa pain

    itsa pain member

    what kind of a barrels does that? I had a colt h-bar 1x7 20 inch barrel that shot 52 grain bullets into tiny bolt action size groups. you cant over stabilize a bullet. only thin jacket explosive varmint bullets come apart when spun at 1x7
  15. MattShlock

    MattShlock Well-Known Member

    1/7? 62 minimum.
  16. Robert

    Robert Moderator

    Mine shoots 55gr, 62gr, and 69gr just fine.
  17. Arizona_Mike

    Arizona_Mike Well-Known Member

    You want the bullet to turn so that it will stays parallel to the bullet path which is an arc. An overstabalized bullet will try to stay gyroscopicly alligned with the barrel and will end up pointed somewhere in between. This small angle between the bullet pointing direction and movement direction causes excess drag and turbulance.

  18. gotigers

    gotigers Well-Known Member

    At what distance? All of it shoots fairly well at 100 yards. What about past 300, 500, etc?

    I feel a good quality heavy match bullet is the way to go for longer distance. The heavier bullet's retained energy for resistance to cross wind is a big help. The 1:8 and 1:7 twists will have a better chance at good results with the heavier ammo.
  19. john wall

    john wall Well-Known Member

    The 77 gr SMK w/c is a game changer past 300 yds in your rifle.

    If you are going to shoot beer cans at 50 yds, anything will work.

    For serious chores, Sierra's 77 gr offering is the way to go.
  20. MtnCreek

    MtnCreek Well-Known Member

    Why w/c? Standard (non cannelure) 77smk's and 75 HPBT's seem to do a fine job in AR's. Have you had problems w/ them or just using the cannelure bullets as an extra precaution?

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