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Advice on barrel twist

I have pretty much decided on purchasing a Savage model 12 VLP, chambered in 223.

It will be used for target shooting only from 100 to 300 yds. Eventually I would like to shoot it up to 600 yds.

I need to decide if the twist rate should be 7 or 9. I am leaning to the 7 inch twist, only because my AR has a 9 inch twist.

Which twist rate would you recommend?

Any help is appreciated.
Mark
 
As target shooting is your intended goal AND your eventual reach is out to 600 yards, I'd say the 7-twist is a no-brainer.

IF the throat's long enough, you can use anything 80-grain & heavier, a decided advantage for a target-only rifle beyond 300 yards.
 
And welcome to the best forum on the web.Please ask more questions,its what we crave,LOL
 
CarolinaBrass said:
Go 1/7 it will stabilize heavier bullets out to longer distances. If it's good for the military it's good enough for me :)

The only reason the military uses a 1:7 twist is to stabilize the long M856 tracer round. A 1:9 is quite sufficient to stabilize the M855 62gr bullet. I actually prefer a 1:8 or a 1:77 to stabilize my long 80 grain bullets, but that twist is not an option in the Savage.

Also, if a bullet is statically stable at the muzzle it will remain so and actually become increasingly more stable as it goes down range; the spin remains the same throughout the trajectory but the forward velocity diminishes which is why the bullet gets more stable. Until it goes transonic where it may get upset, so to speak. In fact the 1:7 twist is too fast for any bullet 80 grain or less but not fast enough for the 90grs; the 1:8 is a better twist, if you can get it.
 
Bayou shooter,

Could you please explain to me why a 1:7 twist is to fast for any bullet 80gr or lighter. I would just like to learn something new.
 
And I would like to know why the 7 twist isn't fast enough twist for the 90's? The only configuration that I know of that would need a faster twist than a 7 twist is a Service Rifle and shooting the Sierra 90's.
 
Froggy,

Good point, I actually know someone who shoots 90 gr bullets out of his 7 twist Krieger and it shoots great. Also if you talk to the ballitisician at sierra they will tell you that their 90 gr SMK will stabilize in a 7 twist.
 
boltman223 said:
Bayou shooter,

Could you please explain to me why a 1:7 twist is to fast for any bullet 80gr or lighter. I would just like to learn something new.

Certainly. We will look at it from two viewpoints; military and target. But first let me simply make this assertion. The twist rate of a barrel should match the intended bullet and usage but if you do not know which bullet you will be using it is better to err on the side of more twist.

From a military POV, the very fast twist rate causes the bullets to be highly statically stabilized at the muzzle and they only become more stable as the distance increases and the forward velocity diminishes. The original twist in the M16 was 1:14 and it was increased to 1:12 to handle arctic conditions. The M193 ammo had a 55gr FMJ-BT which was designed to destabilize rapidly in the target and start overturning and break at the cannelure thus increasing the wounding effect. When the military switched to the M855 with its 62gr SS-109 type bullet, they selected a twist that grossly overstabilized the bullet thus negating a large portion of its terminal effect in the target. This was reported in the after action report following the battle of Mogadishu (Black Hawk Down,) by several participants who related how their bullets would just go right through the emaciated bodies of their adversaries, like needles, causing little damage.

From a target shooting POV, it is well-known that one should use the slowest twist required to statically stabilize the bullet. In earlier times when bullet manufacturing was not as good as it is today, it was very possible to shoot a defective bullet, which would cause said bullet to develop a dynamic instability when fired and make it deflect a little or a lot from its intended trajectory. This issue would be exacerbated by faster than needed twists and on this very site, we discussed such an issue a few months back. The fast twist damaged a thin-jacketed bullet which then flew off course and when the temperature rose, the bullets simply exploded before reaching the target.

I will state that I do not subscribe to the theory that an overspun bullet will keep a nose-high attitude, I believe a statically stable bullet will keep point on during its trajectory. I do not know if there is more pressure or faster barrel erosion due to a faster twist but I do not believe in getting something for nothing; spinning a bullet faster uses energy but it’s probably an infinitesimal amount.
 
boltman223 said:
Froggy,

Good point, I actually know someone who shoots 90 gr bullets out of his 7 twist Krieger and it shoots great. Also if you talk to the ballitisician at sierra they will tell you that their 90 gr SMK will stabilize in a 7 twist.

Who am I to argue with Sierra? So at their website, for stock code 9290, the 90gr .224 SMK, it is stated:

Please Note!! This bullet requires at least a 1x6.5" twist barrel.

https://www.sierrabullets.com/store/product.cfm/sn/9290/224-dia-90-gr-HPBT-MatchKing
 
My bad I should have said may stabilize in a 7" twist. The ballistician said if I can get my velocity up enough the May stabilize and that it is worth a try. He also said velocity is not a cure all.

Bayou shooter since you said that a 7" twist is too fast for anything 80gr or lighter may I ask you why sierras web site says "requires 1x7 to 1x8 twist for the 80 and 77 gr SMK's and for the 69 gr SMK's the box says use only 7" to 10" twist barrels only?


bayou shooter said:
boltman223 said:
Froggy,

Good point, I actually know someone who shoots 90 gr bullets out of his 7 twist Krieger and it shoots great. Also if you talk to the ballitisician at sierra they will tell you that their 90 gr SMK will stabilize in a 7 twist.

Who am I to argue with Sierra? So at their website, for stock code 9290, the 90gr .224 SMK, it is stated:

Please Note!! This bullet requires at least a 1x6.5" twist barrel.

https://www.sierrabullets.com/store/product.cfm/sn/9290/224-dia-90-gr-HPBT-MatchKing
 
boltman223, please reread my longish explanation above. A 1:7 twist will statically stabilize anything up to 80 grains or so in standard length barrels, but they will spin the bullet faster than required and that may lead to some issues as I described above. There is no need to spin these bullets that fast, but given the choice between a 1:9 and a 1:7 and wanting to shoot the longer heavier bullets, you want a 1:7 not a 1:9.

Many of the ARs come with a 1:7 twist barrel, because that's "milspec" and yes, the bullets you mention will stabilize properly in those barrels. 1:8 twists, arguably the best twist for a .223, are fairly rare, found only in match guns usually. And these are certainly not "milspec," so nobody asks for those, the attitude being "if 1:7 is good enough for the military, it's good enough for me."

As for velocity, yes, you can certainly make up for a not quite fast enough twist by increasing the velocity and thus the spin rate at the muzzle, but that will only make up some twist and then the increase in the overturning force will require a faster spin and you just can't make it go fast enough. Our favorite batracian is able to make the 90gr bullets stabilize in a 1:7.2 twist because he has a long barrel. If the bullet is stable at the muzzle, he's good to go because as I explained, the bullet only gets more stable the further it goes.

In normal barrels, like 20 to 24 inches, you will not be able to stabilize the 90SMK with anything slower than a 1:6.5 twist, as stated on the Sierra website. Now, maybe the 90 Berger is shorter than the 90SMK and that would help stabilize it, but I have neither of these bullets and I am too lazy to look them up in the bullet database right now.
 
bayou shooter said:
Who am I to argue with Sierra? So at their website, for stock code 9290, the 90gr .224 SMK, it is stated:

Please Note!! This bullet requires at least a 1x6.5" twist barrel.

https://www.sierrabullets.com/store/product.cfm/sn/9290/224-dia-90-gr-HPBT-MatchKing
[br]
Denys, [br]
It's certainly true they recommend that, but Sierra is notoriously conservative regarding barrel twist. I've shot Sierra 240 Matchkings in a 10" twist barrel at ~2600 fps and they shot accurately at 1000. Sierra recommends at least a 9" twist. Berger's 230 Hybrid, .10" longer, has a 10" twist minimum recommendation. They do work well in 10" barrels. So, while Sierra recommends it, likely also is that a 7" twist will work.
 

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