Twist rate- 22-250 AI
I'm about to re-barrel a rem 700 with a heavy target Bbl.(26-28" and 1" muzzle dia.). My question is about the twist rate. My plan is to use heavier bullets, 60 gr. and up. Im familiar with this cal., and twist rates in general. The nosler manual shows 1 in 14 twist, as does the hornady manual. Why do you not need a faster twist like 1 in 9 or so, to stabilize the longer bullets. Does a faster twist reduce the Muz. Vel. if every thing is the same otherwise? THX HAWKSHAW
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The length of the bullet has a great deal to do with it's stability. The longer the bullet the faster the rifling twist required to stabilize it.
There is a mathematical formula/equation out there that is able to predict the stability of a given bullet from it's weight, which equals it's length for all practical purposes. I believe it's called the Greenhill formula. Nonsense knows quite a bit about it, hopefully he will chime in about it.
If you intend to shoot heavy bullets, 1 in 14 not likely to work.0 -
quote:My plan is to use heavier bullets, 60 gr. and up.
How far up?
A 9" twist will surely handle 68 grain bullets and most probably 75s at .22-250 velocity. Anything above that will take some calculating - at a higher level than Greenhill - or the voice of experience.0 -
The Hornady manual No.8 goes up to their 80 gr. with the 1 in 14 twist. I know the Nosler 60 gr Partition will stabilize in this cart. with the 1 in 14, but I thought that would be the upper limit for 22-250 AI. More research I guess. THX HAWKSHAW 0 -
quote:Originally posted by Hawkshaw
The Hornady manual No.8 goes up to their 80 gr. with the 1 in 14 twist. I know the Nosler 60 gr Partition will stabilize in this cart. with the 1 in 14, but I thought that would be the upper limit for 22-250 AI. More research I guess. THX HAWKSHAW
Hawkshaw,
I don't know why they give that information. A 1-14" twist will NOT stabilize 80 gr. bullets.
To me the simple thing is a 1-9" will stabilize 80 gr. bullets from a .22-250 It will stabilize them from the slower .223. So, I know it will work for you. If you are planning on going with 90's at some time in the future, I would get a 1-8" twist. From a .22-250 that will stabilize anything out there.
To verify your findings it's kind of difficult for me to understand why there is a rage of heavy bullets going on in .223 but for some reason, probably due to myth, the .22-250 continues to get twisted in 1-12" or 1-14" Way too slow of a twist for the heavies out there today. The 1-12" will really only stabilize up to 60 gr. bullets. the faster speed of the .22-250 won't make up for the twist required for the longer/heavier bullets. For a while Savage twisted their .22-250's in 1-9" I'm not sure if they are still doing that. It would be a good thing, I think.
As for the formula's there is the Greenhill which is 180 x D sq. / length.
A couple notes: use 150 for bullets slower than 2800 (down to 2000 fps) and D=diameter sq=squared, i.e. .224 sq=.050176
A variation of the Greenhill is the Velocity formula. Which, takes the velocity you shoot at multiplied by a constant. V x .06 x D sq./L
V = velocity
.06= constant
D = Diameter
sq = squared
L = Length.0 -
Look at what the 22 Newton used. A 22-30/06 with 90 gr bullets. You can overstabilize bullets - try to get a 1 in 24 muzzle loader to hit anything with a round ball, much better luck with 1 in 48, 66 or 72. I read once that about 20% of the chemical energy went into spinning the bullet. The 120 mm Rhine? is a smoothbore at like 5200 fps.
Edit: They may go in as round balls but they come out as a squatty bullets. I tried 40 grainers in a Model 70 225 Win. They made a cute puff of gray smoke about 6 feet from the muzzle.0 -
Hawkshaw,
There is a mild dichotomy here which takes a little explanation to make sense of what the manufacturers represent in print.
First of all, the most common commercial twist rate for the .22-250 is 1:14" for the great majority. There are exceptions but that's not what we're discussing. This is because the manufacturers believe that the .22-250 is a 'varmint' cartridge as used by the largest number of shooters. They are catering to the bigger numbers. They figure (and rightly so) that if you want to launch the longer, heavier bullets, you'll develop your own information (including twist rate) and you won't need them to back you up.
So when Nosler/Hornady represents the 60 gr. Partition or some other similar bullet as needing a 1:14" twist, they're very nearly correct. These are short, stubby bullets traveling at a very high velocity so the twist rate can be a tad slower. This twist rate/bullet combination will work for the vast majority of folks shooting at little furry creatures for sport.
When you state 'and up', we're left with a sort of open ended question with lots of potential for interpretation.
I shoot thousands of the much longer VLD bullets in the 80/90 gr. class using several cartridges for testing at 600 and 1,000 yards. The .223 Rem. requires a 1:8.5" twist at the top end and the .22-250 needs a 1:9" or 1:9.5" depending on the velocity variable. I've also shot the 75 gr. AMAX in the .22-250 using a 1:10" twist, achieving superb accuracy.
If your intentions are to use the VLD's at all, you will need the faster twist rate. If you stick with the 60's you can manage with a slower twist.
By the way, bullets are either stable or unstable. Over-stabilized is not a factor because it doesn't exist. We aren't discussing round balls either, we're talking about pointed bullets. I've shot 40 gr. .22 caliber bullets in a 1:6.5 twist and they made nice, neat little round holes in the target just like their longer, heavier brothers.
Best.0 -
nononsense---THX for the input. ESPECIALLY on the over stabilized comment. Most folks seem to think that there is a fine line between stabilized, and OVER stabilized. As you said, a bullet is either stabil, or it isn't. Over stabilized is like saying a tire on your truck is over balanced. I'm going to ca Hornady, and check with them. I'm thinking 9 or 10 twist at this time. THX HAWKSHAW 0 -
OOOOPSSSSS--In fairness to Hornady, regarding there twist rate, I just noticed that they have a foot-note with the heavier bullets noting that they will not stabilize. My appologies to Hornady. HAWKSHAW 0 -
Exactly what is the interest in heavy bullets for 22 caliber rifles? By that I mean anything over 70 Gr. Why not go to a bigger caliber, 25 or 6mm? 0 -
jptatum,
"Exactly what is the interest in heavy bullets for 22 caliber rifles?"
It's not that the bullets are heavier per se, it's that they are VLD (Very Low Drag) or both heavy and long as in aerodynamic (higher BC). These bullets are what we use when we compete at the longer distances on paper targets or steel plates. There are categories in competitions which are limited to just the .223 Rem. and .308 Win. which get fired at 600 and 1,000 yards from the prone position. The VLD-style bullets are a benefit to making sure they get to the target at the longer ranges.
Best.0
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