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.223 bolt action 1:8 to match with my AR?

Discussion in 'Rifle Country' started by DefiantDad, Sep 23, 2012.

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  1. DefiantDad

    DefiantDad Member

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    Thinking of getting a (good quality) bolt gun with the same 1:8 twist as my AR so I can just standardize on the same .223 ammo.

    What is the optimal length I should go for to reach maximum range for the .223? And what might be (a ballpark for) that max effective range with I suppose the heaviest bullets 1:8 can handle?

    (Was told .223 can be more ballistically stable than 5.56 for long-range accuracy due to less power? This true?)

    Any recommendations?

    Thanks.
     
  2. helotaxi

    helotaxi Member

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    Not true. Higher velocity makes for a faster spinning, and thus more stable, bullet.

    I'm not aware of anyone making a 1:8 factory .223 rifle. A 1:7 is available from Savage and it will shoot anything that your 1:8 will. Your other option is to find a Savage .223 action (ignore what barrel it currently wears) and swap in a 1:8 barrel of your choice.

    As far as max range goes, you can stretch the .223 out to 1000yds with the 80 and 90gn bullets. Having a 26" barrel on the bolt gun will wring out some more velocity and make that kind of range more attainable. An 80gn SMK is still supersonic at 1k provided that you can get 2900fps out of it. The 80gn Amax fares even better. Realize that you'll need 35MOA or so of elevation adjustment available to go from 100 to 1000 yds and you're looking at 10 MOA of drift with a full value 10mph x-wind at 1k as well. If I were serious about shooting 1k or thereabouts, I'd certainly not be looking at using a .223 (or .308 for that matter).
     
  3. SpaceMonkey

    SpaceMonkey Member

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    Factory 1:8 twist

    The Tikka T3 comes in 1:8 in .223 if you want the same twist.
     
  4. DefiantDad

    DefiantDad Member

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    Ok thanks - good points and I will check out the tikka also
     
  5. Coltdriver

    Coltdriver Member

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    I have a stainless Ruger in .223, mine is 1 in 9. I have an AR too.

    My Ruger chamber is too tight for 5.56 ammo. I have a lot of Winchester 5.56.

    I checked the chamber and the ogive on the 5.56 ammo I have is far enough forward that the bullet goes in the lands a bit.

    I have had other .223's I could shoot 5.56 in all day. But not the Ruger.

    You may not find a bolt rifle with a 5.56 chamber.

    Never seen one blow up, never seen anyone have a problem including me. But stuffing the bullet in the lands is harder on the rifle.

    Notice too that shooting one out a thousand yards is giving you an artillery type arc.
     
  6. nipprdog

    nipprdog Member

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  7. jakk280rem

    jakk280rem Member

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  8. DefiantDad

    DefiantDad Member

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    Thanks guys, I probably will keep 5.56 for the AR and use the 223 on the bolt. I will check with the LGS on the rifles you have all mentioned.
     
  9. DefiantDad

    DefiantDad Member

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    Thanks but seems like the Mossberg models are all laminate. I wanted synthetic + SS.
     
  10. MistWolf

    MistWolf Member

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    It's easy to ream a 223 SAAMI barrel to 223 Wylde or 5.56 NATO specs. Because of the problems with running 5.56 NATO rounds in a 223 SAAMI barrel, most manufacturers use a more generous leade in their sporting rifles.

    You can have the chamber of your bolt action checked and if the leaded is too short, a light bit of reaming will fix the problem.

    I have a 223 Wylde spec chamber in my AR carbine and it runs 5.56 ammo safely
     
  11. BoilerUP

    BoilerUP Member

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    A 1:9 bolt gun should stabilize 75gr HPBT/77gr SMK just as well as your 1:8 gas gun.

    I've got a 26" 1:9 Savage 12FV barrel (its been on a bunch of different actions...) that shoots exceptionally well with a 75gr HPBT over 24.0gr Varget @ 2860fps...same load also works well in my ARs when loaded to 2.26" (I run it 2.29" in the bolt gun).
     
  12. MistWolf

    MistWolf Member

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    Testing done by Sierra shows otherwise. They found the 1:8 twist stabilized their 69 gr bullet better than the 1:9 and the 1:7 worked even better for the 223.

    However, every barrel is a law unto itself and rifling twists are never exact. Rifling could have greater or lesser twist than advertised.

    Also, twist rate isn't what determines what bullet length it will stabilize. It's the RPM of the bullet. Longer bullets require more RPM. A faster bullet will exit the muzzle with more RPM than a slower bullet when fired from the same barrel. But you'll never know what will actually work until you shoot.

    If you never shoot anything heavier than 55 gr bullets from your 223/5.56, a 1:9 will give you good service at almost any barrel length but a 1:8 twist is more versatile
     
  13. BoilerUP

    BoilerUP Member

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    "Stabilized better"...that's kind of an ambiguous statement.

    Certainly a faster twist will provide more RPMs to the bullet providing more stabilization. But once a bullet is stable, the question becomes this: does greater stabilization means greater accuracy?

    The 'Shooter' ballistic calculator shows a 1:9 twist barrel provides a 77gr SMK @ 2600fps a stability factor of 1.38, assuming 500' ASL elevation and a standard atmosphere. 1:8 twist gives a 1.74 stability factor, while 1:7 is 2.28.

    I think we can all agree that 2.28 is more than 1.38 by a substantial margin...but 1.38 is most certainly stable by a pretty fair margin itself. And once stability is achieved, there's no guarantee that the 'more stable' bullet from a 1:7 will be any more accurate the same 'less stable' bullet at the same speed from a 1:9 barrel.
     
  14. MistWolf

    MistWolf Member

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    In this case, no. Sierra tested the BC of the bullets in flight with a Doppler radar. They found that when fired with slower twists, the bullets had more precession which increased drag on the bullet. The trend was that groups size would open up

    At shorter ranges, the greater precession present at lower RPMs may not be enough to open up group sizes. But further down range, RPMs begin to drop and precession increases. Combined with greater time of flight it can cause even greater deviations to the flight path. I suppose what that really means isn't that greater stabilization gives greater accuracy but that less stabilization hurts accuracy and grouping.

    In real world applications, Service Rifle Match Shooters find that twist rates of 1:7 give better results at 600 with the longer bullets (usually weighing in the 70 gr range which are longer and have better BCs) than the 1:9 twist. Some even use 90 gr bullets and a 1:6 twist
     
  15. helotaxi

    helotaxi Member

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    Actually, what typically happens at longer ranges is that the precession of a bullet that isn't completely stable diverges to the point that the bullet tumbles and groups open wildly if the bullets even stay on target. The real answer is that while the bullet is close to stable at short range, it isn't spinning fast enough to ever really become stable. It may hit point first in close, but eventually diverges to the point where all hope is lost.

    You can get a situation where the bullet "goes to sleep" as the upset force from drag drops faster than the RPM decays (which is pretty much always the case) and the initial oscillation was well damped by spin to begin with. The initial nutation of the bullet increases the drag and the velocity decay, helping to completely damp out the oscillation more quickly. The way to defeat most all of this is to shoot extremely concentric ammo that fits the rifle chamber well and doesn't precess to begin with. If the bullet isn't spinning fast enough in that ammo/chamber combination, it will tumble at some point because the oscillation becomes divergent before the aerodynamic upset force diminishes enough that what spin is there is able to stabilize the bullet.
     
  16. jim243

    jim243 Member

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    Ah, long barrel vs short barrel, speed vs accuracy. A 24 to 26 inch barrel would be the max because after that the powder is fully burned and you start to lose speed out of the longer barrel. The hotter the round the more the barrel heats up and you start to string your shots instead of keeping them in the same place.

    Each is a trade off in what you want to do. The heavier, longer boat tail bullets are more stable at long distance, but you are trading speed for weight. Depending on cross winds at the target distance will deturnmine what weight you will want to use.

    As a suggestion only, I find that a 20 inch bull barrel will give me excelent accuracy with a 75 grain bullet out to 600 yards. The bull barrel will heat up slower and the lighter than max weight bullet will still let me get 2,900 fps speed out of the barrel.

    This is a Savage Model 11 GBT in 223 Remington and is accurate as all get out. It is a 20 inch LE bull barrel on it. The trigger is set to just under 2 lbs with no over travel on it.

    Jim

    [​IMG]
     
    Last edited: Sep 30, 2012
  17. helotaxi

    helotaxi Member

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    It takes a barrel a good bit longer than 26" for that to happen with .223. The rate of increase per inch of barrel length begins to taper off a bit but you're still gaining velocity. A barrel longer than 26" is a little impractical, but it does offer more speed. There is minimal relationship between barrel length and accuracy. With a load that is well matched to the barrel harmonics and a quality barrel that has been well stress relieved, a long barrel can be incredibly accurate and might be required if you need the extra velocity to reach a particular range.

    Not sure what you mean by this. There is no relationship between bullet weight and length and "stability" at long range. Longer bullets usually have a higher BC which means that it will resist wind drift better. At close range the extra velocity of the light bullet can equalize this to a great degree, but once the velocity starts to decay bullet drop and wind drift increase rapidly. Because of the typically poor BC of light bullets, this happens rather abruptly. Most guys that shoot .223 across the course stick with either the 69 or 77gn SMK or the Hornady 75gn HPBT regardless of range because it doesn't handicap them at close range and gives the least wind drift at long range.
     
  18. samoconnor123

    samoconnor123 Member

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    The Tikkas are a brilliant rifle, mine certainly is.

    You could see if you can get a DeLorean and travel at 88mph and go back to when you first got your AR and get one with a Wylde chamber so you can shoot both 5.56 and 223 ammo.
     
  19. DefiantDad

    DefiantDad Member

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    With the option to time travel I am sure we can open up another whole new thread to discuss exactly what we should get :)
     
  20. helotaxi

    helotaxi Member

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    Unless his AR is one of the very rare breed truly chambered in .223 he can already fire both.
     
  21. MistWolf

    MistWolf Member

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    That's what I said. Point being, if you are shooting 55 grs* or less, or shooting 69 gr* bullets at close range, say 250 yards or less, a 1:9 twist will work. But if you're shooting longer ranges or shooting heavier* bullets (or both), choose either a 1:8 or 1:7. The tests performed by Sierra supports this

    *I used the weight of the bullet for simplicity. The reality is that it's bullet length that matters. Shape and material density can give the shooter a heavier bullet that's short or a lighter bullet that long. As most bullets are lead & copper and use similar profiles, weight can be used for generality
     
  22. Cee Zee

    Cee Zee member

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    I shoot my Savage 12 LRPV with a 1:9 twist over 400 yards using 75 gr. bullets with no problems at all. In fact it is very accurate at that distance. I'd like to shoot farther but that's the limit at the gun club. But it will do 2" groups with heavier ammo at that 400+ yard distance. For the most part it does better with ammo at about 68 gr. up to 75 gr. although I've seen a rare box of 52 gr. ammo do very well too. Mostly the lighter stuff gets blown around by the wind more.

    BTW I have a 26" barrel on the Savage. The people at the Savage board claim that's the best barrel Savage makes for their rifles. Anything longer makes the rifle front end heavy and hard to balance well.
     
  23. MistWolf

    MistWolf Member

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    Every barrel is a law unto itself. Barrels are almost never the exact twist as they are listed as having and, depending on how they are made, twist can vary from barrel to barrel. With a 26 inch barrel, velocities are higher than the common 16" or even 20" AR barrel. This means the bullet exits at a higher RPM and the reality is, RPM is what stabilizes the bullet
     
  24. helotaxi

    helotaxi Member

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    And my 12FV shoots the Hornady 75gn HPBT just fine in a load that is 2gn below published start loads with AA2520. Velocity might equal the starting load (velocity numbers are from a 24" barrel in the data) but I doubt it. Haven't bothered to shoot it over the chronograph simply because I moved to the Nosler 69gn Custom Comp which I can get significantly cheaper. Both my 12FV and 1:9 16" AR shoot those loads fantastically well out to 400yds.

    If 55gn bullets are having stability problems at long range it's either a crappy bullet or having transonic stability issues. Barrel twist has nothing to do with it.
     
  25. MistWolf

    MistWolf Member

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    Twist and velocity equal RPM. RPM is needed to stabilize bullets. Sierra has found that too little RPM has a negative impact on the BC of a bullet because of nutation. They found that higher RPMs result in less nutation. Twist does have something to do with it. So does velocity

    Again, every barrel is a law unto itself
     
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