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223 Bullet weights for 1:7 twist

Discussion in 'Rifle Country' started by dalepres, Sep 19, 2011.

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  1. dalepres

    dalepres Member

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    I have a new, unfired so far, AR-15, home built. It has an 18-in 1:7 twist barrel. I know it can handle heavier weight bullets but what is the best, safest, and reliable weights for the lower weight bullets? Should I expect it to shoot 52 to 55 grain ammunition reliably?

    Thanks,

    Dale
     
  2. FlyinBryan

    FlyinBryan Member

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    you should have no problems with any bullets from around 50 grains and up.

    i think a pretty good rule of thumb is 1/7 for bullets of 50 grains and up, and for 1/9 70 grains or less.
     
  3. midtennpawnstar

    midtennpawnstar Member

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    I have a Bravo company/spikes tactical ar i put together and i went with the 1:7 primarily because i have a ton of 62gr pmc lap, from what i know thats the primary grain in mind with the 1:7 but like FlyinBryan says 50 grains and up your good....dont really want to go lower because your varmint loads like 45gr and lower could tear up with a tight twist.......happy shooting!
     
  4. Tape

    Tape member

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    1:7 Twist 62-77 grain range
     
  5. ugaarguy

    ugaarguy Moderator Staff Member

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    1:7 twist will shoot any .223 / 5.56 bullet up to 77 grains. You can't over stabilize a bullet. If you decide to shoot very thinly jacketed bullets (typically marketed as varmint bullets) weighing less than 55 grains in a 1:7 twist bbl. keep velocity under 2800 fps to prevent tearing the jacket.

    M855 is 62 grain FMJ with a steel penetrater core. M193 is standard 55 grain FMJ. The M16A2 has a 1:7 twist barrel.
     
  6. Tape

    Tape member

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    #of fps; glad you brought that up because many I have told say I'm full of it, that is the reason I didn't mention it, don't feel like bickering. I tell people that if spun to fast it can fall apart before it gets to the target.
     
  7. Red State

    Red State Member

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    What uagaarguy said.

    55gr will be fine all day long, but 62gr will probably be better.
     
  8. ugaarguy

    ugaarguy Moderator Staff Member

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    Yep, it's right there in the Speer Reloading Manual (and probably others). I'm sure they just made it up :D .
     
  9. helotaxi

    helotaxi Member

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    It depends on the particular bullet. The Speer TNT and Hornady SPSX are particularly fragile and run the risk of gyroscopic failure. The Sierra Blitzkings and Hornady V-Max can have the crap driven out of them without issue. I've also loaded some screaming Varmint Grenades (36gn) from my 1:7 and they held together fine and were fairly accurate.
     
  10. mshootnit

    mshootnit Member

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    Are there any weight 22 cal projectiles that 1/8 won't stabilize?
     
  11. supercalvin56

    supercalvin56 Member

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    I have a 7 twist 223 that shoots anything....even the 40 grainers. Try it, I'll bet you never have a problem, I haven't
     
  12. FlyinBryan

    FlyinBryan Member

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    i used to doubt people that said this until i lost a support rod and a sunshield on my chronograph because one poofed right between the chrony eyes.

    it was last thanksgiving and we were shooting 45g bullets out of a 1/7. i was loading them @3500+ with varget.

    i thought my chrony shorted out because it looked like sparks shooting out of it.
    (shooting chrony has great customer service because i called them much later, like 6 months, and told them what happened, the truth, and they sent me new stuff for free.)
     
  13. rori

    rori member

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    Why have a 7 barrel if you don't want to shoot heavy bullets. My minis are 9's and I wish one of them was a 7 so I could run heavier bullets than the 65's I run now. Frank
     
  14. Robert

    Robert Moderator Staff Member

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    I shoot 55gr bullets, both factory and hand loads of unknown velocity, in my 1:7 rifle with 0 problems. I have never had a 55gr bullet come apart before reaching the target. Ever.

    55gr though 77gr should be fine in any reliable AR. I have a bunch of 62gr waiting to be loaded up. But I shoot at ranges up to 600m and like the heavier bullet.
     
  15. TonyAngel

    TonyAngel Member

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    In answer to your question regarding 52 and 55gr projectiles, you won't have any problems with those. Actually, I'll say that you shouldn't have any problems with those. I really like the 52gr projectiles from Sierra and the 55s from Hornady and have had good results with them for ranges out to around 300 yards or so.
     
  16. UKWildcats

    UKWildcats Member

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    Here is some good information on maximum bullet weights versus barrel twist -- http://www.6mmbr.com/223rem.html

    Just be carefule shooting light bullets fast -- the jackets can be too thin to handle the spin rate and will fall apart in flight.

    UK
     
  17. wingman

    wingman Member

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    I've owned 4 or 5 223's they all preferred 52gr match @100 yards. Honestly while it may be a 1/7 or 1/9 twist never know what it will shoot best until trying, but the 52 Berger match or 52 sierra has always been the most accurate for me.
     
  18. helotaxi

    helotaxi Member

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    You can file all that in the BS department. Accuracy is a factor of barrel quality and matching a load to barrel harmonics. Unless you've tried to tune a load with a quality bullet to your rifle, you can't say that 55gn bullets won't shoot from your rifle. All you can say is that the loads you tried were not accurate. If you're talking about mil-type 55gn loads, the bullet itself was the cause of the poor accuracy, not the weight but the consistency (or lack thereof). I've shot from 36gn to 75gn bullets from my ARs (with both 1:9 and 1:7 twist) with acceptable accuracy and no bullet failures with modern style varmint bullets (not Speer TNT or Hornady SPSX). I've never made an effort to keep the velocity down either.
     
  19. dc.fireman

    dc.fireman Member

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    Dalepres - I shoot Hornady 68 gr. BTHP's, and Sierra 69 gr. HPBT's, loaded over Varget powder. I'm currently working on a load for Nosler 77 gr. BTHP's. You'll be fine in the twist rate department for the heavier weight bullets. I think where you may run into a problem, is if you attempt to go with something which requires a longer-than-magazine length load (which for an AR-15, is slightly over the 2.260" mark). I forget if it's the A-Max, or V-Max - but one of the Hornady 75 gr. bullets may cause you problems if you decide to load it for the AR. The long bullet ogive, doesn't go well with the magazine length requirement. You can load them, and shoot them in single - fire fashion, just not from the magazine (easily, at least).
     
    Last edited: Sep 21, 2011
  20. Hocka Louis

    Hocka Louis Member

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    Flyin Bryan has it backwards. Tape is right.

    1:7 is NATO for heavy heads about 62 up to and including 77 gr. tracer rounds. Those who have them get defensive about it and claim they'll do everything. OK Sure. Colt pushed them on the civilian market. If you have 1:7 forget buying less 62 gr. bullet ammo -- it isn't for you.

    Someone mentioned a BSM -- my stainless target carbine is 1:8. They know better shooters are going heavy but never 77 gr. heavy! I could also make do with 55 in a pinch.

    1:9 is kinda univesal 55 - 62.

    Wanna shoot 55, and/or 55 or less!? 1:9 or SLOWER twist if you can. The original was 1:14, then 1:12. 1:11 you'll sometimes see for 55 and lighter as well. Even 1:10.
     
    Last edited: Sep 20, 2011
  21. ugaarguy

    ugaarguy Moderator Staff Member

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    I guess US Army FM 23-9 is lying. The M16A2 (1:7) shoots M193 (55 grain) as well it shoots M855 (long 62 gr steel core), and as well as the M16A1 (1:12) shoots M193.
    Never 77 gr? That's a bold statement. Black Hills sold so much Mk 262 Mod 1 (77 gr SMK w/ cannelure) overrun ammo that they started offering it as a standard item being sold 5.56 77 gr OTM.
    Or you could say 1:9 is too fast for really thinly jacketed light bullets, and too slow for the really long (aka heavy) stuff. (Unless you have an exceptional 1:9 twist bbl. like one member here which will stabilize the 77gr stuff).
    Again, 1:7 twist is just as accurate as 1:12 with 55 gr. FMJ, or other moderate to thick jacket ammo.
     
  22. Robert

    Robert Moderator Staff Member

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    So the over 500 rounds of 55gr I have shot at steel, and hit for the most part, out to ranges of 400+m are just all a fluke? Cool! I like it when I defy the laws of the universe.
     
  23. TonyAngel

    TonyAngel Member

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    Man, lots of bad information flying around in here. I wonder how many of the guys posting that you can't shoot a 55gr and under bullet out of a 1:7 twist rifle are speaking from experience. If they are speaking from experience, what did they miss when experience was speaking. If they had a rifle that tore a varmint bullet apart, what brand/type of bullet was it? If they had a rifle that wouldn't shoot 55gr bullets accurately, again, what brand and type of bullet was it; and was it true of one rifle or more than one rifle.

    The fact of the matter is that you won't know if a particular bullet will shoot in your rifle until you work up a load for it and see. I've had several 1:7 twist barrels that showed a real preference for 52gr HPs at shorter distances.

    BTW, the twist needed to stabilize a bullet is NOT dictated by the bullet's weight, but its length. There are longer bullets out there that are lower in weight, but require the faster twist rates due to their length. A good point of comparison is the Sierra 77gr SMK and the Hornady 75gr A-Max. I've had 1:9 barrels that would shoot the SMK pretty well, but wouldn't shoot the A-Max at all. The A-Max is a long bullet and cannot be loaded to mag length. I've never been able to get the A-Max to shoot in anything slower than a 1:7.

    I do, however, have to admit that I have a theory and have speculated that a 1:9 twist barrel would shoot crappy 55gr bullets better than a 1:7 will. This is only based on the fact that cheap bullets aren't always perfectly round or balanced like good/expensive match bullets and will have a wobble to them, which is exacerbated by the increased rotational speed of the faster twist. It's just a theory and haven't given anything more than thought to it because I usually shoot match bullets when I'm looking for accuracy.
     
  24. FlyinBryan

    FlyinBryan Member

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    lol @ hocka
     
  25. ugaarguy

    ugaarguy Moderator Staff Member

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    THR member rsilvers alluded to that in a recent .22 LR bbl. twist thread. He does something with weapons development at AAC (based on his posts in the 300 Blackout Threads), and he seems to know his stuff. I think your theory is sound, and probably has been proven. Based ATK's technical bulletens, and the documentation in FM 23-9 I'd wager that US M193 ball is near perfectly round, and well balanced.
     
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