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Thread: WHAT is the perfect bullet wt. for a .223 with a 1 in 9 twist.

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    Default WHAT is the perfect bullet wt. for a .223 with a 1 in 9 twist.

    AR-15 with a barrel has 1 n 9 rate of twist, what is the perfect (Range) bullet weight...? Will it stabilize a 77 Gr. bullet........?

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    In my experience, 1 in 9 is generally good for up to about a 69 grain bullet. More or less 55-69 stabilize alright. For a 77 grain bullet, I think the preference is 1 in 7 or at least 1 in 8.
    NRA Life Member, Prior F-16 crew chief.

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    The length of a projectile has more effect on how it stabilizes in flight than the weight. Obviously, the heavier a bullet is, the longer it is likely to be. Some exceptions occur: Varmint Grenades, and MPG's are long for their weight because they contain no lead, just a compressed, powdered metal core. My AR has a 1:9 twist and likes 55 grain bergers, 50 grain Varmint Grenades and other 45-55 grain bullets. It shoots sub MOA with the Bergers. I cannot get the 55 grain MPG's to shoot well. I think it is because they are very, very long for a 55 grain bullet. Try 23-25 grains of 2230 with a regular 55 grain FMJ. Once you find the load your gun likes, you'll be surprised how well it shoots with cheap bullets. I buy the Remington FMJ's for $10/100.

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    I expected this thread to have taken off by now, and was very interested in where it might go. Also, I am not sure how many different 2230's there are out there, but I was refering to Accurate brand 2230.

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    Yes, I thought there would be lots of responses to this. I just ordered a Rock River and it is 1 in 9 twist. And I don't want to reload for it, but I was hoping it would stabalize the 69 & 77 Gr. bullets. I f not I'll just use bulk 55 Gr. factory reloads.

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    You'll be surprised how well an AR with a good barrel will shoot the cheap stuff

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    I've got a nice SS barrel in 1-9 and it loves to throw the 69s. I use RL15 for these. I've burned a lot of AA2230 for the 55s and it is my go to powder for the 55s.

    All you can do is try the various weights in YOUR rifle. Seems some will and some won't. Might try the Hor. 75 too.

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    has anyone managed to get the 55 grain MPG's to shoot? It says 1:9 or faster on the box, but my bushmaster (1:9) hates them. I've probly blown at least a hundred bucks trying to get those stupid things to group better than 3"

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    Member tyrex13's Avatar
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    I've had good accuracy with 55gr-69 gr in all my 1-9"s. I have not shot 75's or 77's though so can't offer anything info on those. The worst you could do is buy a box and see how they fly.

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    Quote Originally Posted by sthrcave View Post
    The length of a projectile has more effect on how it stabilizes in flight than the weight.
    +1. Not many folks make that correlation. For 55's try H322.

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    Yup yup.

    55 grain bergers do nasty things to bunnies and grouse.

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    I,m fairly sure my Ruger Ranch rifle is 1:9 twist and you guys know how they (most) Shoot. Mine is no exception...........4-6" groups @ 100 yrds with military surplus and Wolf 55 grain. However, the 69 and 77 grain Black Hills (blue box) did much better, 2" to 2 1/2" @100 yrds. Seemed like there was no preference b/t the 69 or 77 gr.

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    I bet if you started handloading you could tighten those groups up significantly.

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    Quote Originally Posted by sthrcave View Post
    You'll be surprised how well an AR with a good barrel will shoot the cheap stuff
    I don't think I'll be supprised........

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    Good stuff Murphy, with my 1 in 9 twist 18" barrel on my S&W AR-15 I stick with the 55gr Sierra although it will stabilize the 60gr Sierra.
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    Quote Originally Posted by Murphy View Post
    Both velocity and twist rate help stability.
    Yes, because both affect the bullet's RPM.

    Quote Originally Posted by Murphy View Post
    The 1 in 9" twist will stabilize the 69 grain lead core match bullet from Sierra (and it is long) with a muzzle velocity of 2800 fps and it will remain accurate out to 600 yards. 16" guns probably can't maintain stability of this bullet with a 1 in 9" twist.
    I never thought of a 1:9 twist to be "on the fence" for stabilizing the 69-grainers, such that 4" of barrel length would cause such a dramatic effect.

    I have shot longer bullets than the 69gr SMK's, seemingly with ease, out of a 1:9 twist. The Hornady's 75gr BTHP's and 75gr A-Max's (a very long bullet) shot just fine out of my Kimber Montana's 1:9 twist. But, I don't have the velocity figures on-hand to make an accurate comparison between a 69gr SMK fired out of a 16" AR barrel and a 75gr A-Max fired out of a 22" barrel. So, admittedly, any comparison I make is purely conjecture.

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    Quote Originally Posted by Dan in Alaska View Post
    Yes, because both affect the bullet's RPM.


    I never thought of a 1:9 twist to be "on the fence" for stabilizing the 69-grainers, such that 4" of barrel length would cause such a dramatic effect.

    I have shot longer bullets than the 69gr SMK's, seemingly with ease, out of a 1:9 twist. The Hornady's 75gr BTHP's and 75gr A-Max's (a very long bullet) shot just fine out of my Kimber Montana's 1:9 twist. But, I don't have the velocity figures on-hand to make an accurate comparison between a 69gr SMK fired out of a 16" AR barrel and a 75gr A-Max fired out of a 22" barrel. So, admittedly, any comparison I make is purely conjecture.
    Unless at times we shoot the bullets longer than the 69grSMK at distance past 200yds it is hard to tell if the bullet really is stabilizing well. I have shot longer bullets out of my 16" barrel with 1 in 9 twist and at 100yds things looked pretty good but at longer ranges the groups were not what I expected from the initial evidence I had at the 100yd mark.
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    Member Dan in Alaska's Avatar
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    It's my understanding that if a bullet is "stabilized" when it leaves the muzzle, it will be "stable" for the remainder of its flight, or at least until it slows down to the point of slipping sub-sonic. Furthermore, as a given bullet progresses further in flight, it becomes MORE stable, not less stable.

    Dan Lilja explains it fairly succinctly, so I'll let his words explain it. An excerpt:
    If a bullet is fired from a barrel that has no rifling, the force exerted on the nose of the bullet by the air will cause it to flip over and its trajectory will be wild.

    To overcome this tendency, a bullet is spin-stabilized by rotating it about its long axis. The amount of spin required is determined by the specific gravity, shape and construction of the bullet, bullet velocity, and the density of the air it is going to travel through.

    It is interesting to note that this force, or overturning moment, acting on the bullet nose is greatest when the bullet first exits the barrel. If a certain bullet-barrel combination will stabilize a bullet at the muzzle, the bullet will remain stable for the rest of its flight. Why is this so? As a bullet flies on toward the target and beyond, it is losing velocity rapidly as any trajectory table will show....

    ....The rotational speed of the bullet or its RPM's decreases at a much slower rate. The overall result is a lessening force acting on the bullet nose, and that force is being overcome by a proportionately greater spin rate compared to forward velocity. The down-range bullet therefore is more stable than it was at the muzzle. The only exception to this occurs when the bullet passes through the speed of sound. At that velocity, about 1180 fps, it may lose stability.

    Beartooth, if you're getting round holes at 100 yards, the bullet is stable. For an explanation of larger groups at longer ranges, I would look at factors other than your barrel's twist rate.

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    Like most of us, I am still learning and seems I have much to yet learn. I guess the factor I need to look at is me the shooter? Guess I am not as good a shot as I assumed? Of course I might be a good enough shot that since the bullet is covering the 100yds in much less than a second, that it would take me shooting at longer ranges to realize I don't really have that accurate of a load due to lack of stability. Makes you wonder, I know it makes me wonder?

    Point in case, I can shoot the same bullet like the 208gr Amax in my 300win mag and drive a good 130fps slower than with an other powder using the same bullet and both give me around a half inch at 100yds but one of those loads does not shoot as tight at 600yds by as much as 3" difference in the group size as appose to the other. This happens with both loads on a consistent bases over three five shot groups at that distance, so that pretty much rules out the idea that I am doing a better job of shooting one group as apposed to the other group. Just wonder if it has anything to do with stability of the slower bullet. Now when those bullets leave the end of the barrel it can't be blamed on me or the rifle after that point since my consistency at 100yds and consistency at 600yds with both loads is the same. Sure makes you wonder, it does make me wonder?
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    Member Dan in Alaska's Avatar
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    Beartooth, with regard to your given two 208A-Max loads, what were the shot-to-shot velocity differences (also called extreme spread, or ES) for each load? You mention the velocities, so I'm assuming you chronographed them. How consistent were they?

    I'm thinking that your 600-yard accuracy woes might have more to do with a larger ES, than how the particular loads groups at 100 yards.

    I had a friend that shot 1000 yard matches, back in Wisconsin. When he developed a load, he relied heavily on the chronograph readings, rather than the 100 yard target. Even a 50fps ES can have a profound effect on long range groups.

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