Different twist on .223 rifles...which one ?


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Blue
October 14, 2004, 10:40 PM
Going to buy a .223 for a predator rifle, and plan to shoot 40-45-50 grain bullets. I am a ballistic novice, but from what I have read "the lighter the bullet the slower the twist" is the rule.

The Savage .223's have a 9-1 twist.
The Remington's, Ruger's,Weatherbys have a 12-1 twist in the .223.

Should I stay away from the 9-1 twist Savage if half of my shooting will be with the 40-45 grain? :confused:

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Coltdriver
October 14, 2004, 11:34 PM
I have a Ruger Number 3 in .223

It has 1 in 12 twist.

It is made for bullets up to 55 grains. Over 55 grains and you may run into some problems stabilizing the bullet.

With any bullet under 55 grains the 1 in 12 is preferred over the faster twist.

You may actually find that a 1 in 9 twist shooting a hotly loaded 40 grain bullet causes the bullet to vaporize due to spinning it too fast.

I would find a 1 in 12 twist for the lighter bullets.

MrMurphy
October 14, 2004, 11:48 PM
It's 1-in-whatever... what you said was 9 turns in 1 inch! :)

It's listed as 1 turn in so many inches.

Dave R
October 14, 2004, 11:54 PM
If you want to shoot the heavier bullets in .223--62gr. and up--you need the 1 in 9 twist. OTOH, at high velocities, some of the ligher varmit bullet may come apart with a twist that fast.

For the lighter bullets--up to 55gr--the 1 in 12 or 1 in 14 is fine.

My AK in .223 will "blow up" Winchester's 45 gr. varmit bullets. Not every one, but maybe 1 in 3. It has a 1 in 8.5 twist. I have an NEF in .223 with a 1-in-12 twist. It shoots bullets light bullets up to 55 grains very well.

JohnKSa
October 15, 2004, 12:28 AM
1:12 twist will work up into the light sixties. If you plan to shoot bullets lighter than 60 grains exclusively then you can probably get better velocity and longer barrel life out of a slower twist barrel like the 1:12.

Thompson Center's .223 barrels are also 1:12 twist.

GLOCKME
October 15, 2004, 01:30 AM
So what is the best grain for a 1 in 7 twist??

DMK
October 15, 2004, 08:58 AM
So what is the best grain for a 1 in 7 twist?? The present military rifles are 1 in 7. They changed the twist from 1 in 12 to 1 in 7 to shoot 62gr. M855 ammo (where the older M16A1 used a 1 in 12 for 55gr M193 ammo). So anything from 62gr. on up should work fine. I've seen Army manuals that state 55gr. will work for practice and emergency, but it's not generally accurate enough to be issued with these twist rates. YMMV.

Like any other gun, buy a box each of a few different types, shoot the rifle off a rest and see what groups the best. I have a 1/9 AR that throws 52 gr. all over the place, groups 55gr. OK, dislikes 68gr. but shoots 75gr. really well. Go figure.

ny32182
October 15, 2004, 09:29 AM
I've shot 55gr through my new 1/7 with good results.

I've heard that the military 1/7 twist was a bit of a compromise: 1/9 is perfect for 62gr M855, and something slightly faster was best for the "new" tracer round (don't remember the designation), and that 1/7 was settled on as the best compromise. Like I said in my so far brief experience with 1/7, it shoots 55gr fine so I suspect it would work great for anything heavier than that. 55gr is the lightest I would try in it though.

My 1/9's shoot 55 fine of course, and I wouldn't hesitate to try lighter rounds in there. Personally I wouldn't go 1/12 just because of the restriction to 55gr or less. 1/9 should let you go from 40 to somewhere in the high 60's if you want.

Jim Watson
October 15, 2004, 10:21 AM
My old 1-12 Rem 788 shoots 60 grain Bergers better than anything else, but they are flatbase. I don't know if it would handle a 60 gr boattail, but I don't care. My 1-14 .22-250 shoots 60 grain Hornadys as well as anything lighter, but its higer velocity adds a little stability, the rpms are about like a .223 1-12.

My 1-9 AR shoots 52 grain Sierras best.

GOOD barrels and GOOD bullets are pretty flexible if there is enough twist for stability at all.

I don't know about the really light stuff.

mete
October 15, 2004, 01:41 PM
Technically the twist relates to length not weight .A longer 50gr spitzer needs tighter twist than a 50gr round nose.

HKrazy
October 15, 2004, 01:41 PM
It amazes me just how fast .223 bullets spin.

If the bullet leaves the muzzle at 3200 fps here is how fast it is spinning:

1/12 twist = 192,000 RPM
1/9 twist = 256,000 RPM
1/7 twist = 329,143 RPM

You can see why 1/7 can disintegrate some bullets.

KW
October 15, 2004, 01:48 PM
From my own experience, 1/9 twist will stabilize anything up to 69gr. Some people have had some sucess with heavier rounds in their 1/9 barrels, but accuracy wasn't acceptable to me with these heavier rounds.

My new 1/7 twist upper will shoot 55gr just fine all day long, and will handle the heavier 75 and 77grn rounds.

Both of these were 16" barrels.

Harry Tuttle
October 15, 2004, 04:01 PM
http://www.ammo-oracle.com/body.htm#twists

Q. OK, what is all this stuff about rifle twists and different ammo?


Rounds in flight spin for stability because of the rifling on the inside of the barrel._ Depending on how much they spin, they are more or less stable in their flight and therefore more or less accurate._ The earliest AR15s from the early 1960s had a twist rate of 1 complete twist every 14", or 1:14._ This was increased to a twist rate of 1 turn in 12" for the M16, XM16E1, M16A1, and later rifles and carbines._ The current M16A2s and up and the M4 carbines have a much faster twist rate, 1 turn in 7"._ The reason for the 1:7 twist is mainly to stabilize the M856 tracer bullet, which is much longer than other bullets._ You will recall from above that the M856 was designed to provide 800 meters of trace out of the SAW.


While the slow 1 in 12" twist is adequate to stabilize the 55 grain M193, it will not stabilize the 62 grain M855._ As a result, the newer M855 ammo will group 1-2 feet at 100 yards, with bullets flying through the air sideways, instead of shooting to about 2" at 100 yards, like military ammo should.


All this has some ramifications for ammunition selection depending on your rifle's rate of twist.

JohnKSa
October 15, 2004, 09:35 PM
One point that has not been addressed---the M855 is a steel core bullet and therefore LONG for its weight.

Generally a 1:12 twist should stabilize a lead core 62 grain bullet especially in a long barrel (more velocity and therefore faster spin.)

In a short barrel or in a long for weight bullet you'll probably have to go to a faster twist than 1:12 to get up into the 60 grain bullets.

Faster twist than you need won't usually hurt accuracy. It will cut down barrel life and in extreme cases it can cause the bullet to lose integrity (come apart from centrifugal force.)

Frohickey
October 15, 2004, 10:03 PM
The 'vaporization' of bullets is more like disintegration of the bullet. Its usually because of inadequate jacket thickness for the bullet spin. That is why .224 bullets made with 22LR cases are supposed to be driven slower than other bullets. The 22LR brass cases are thinner than the 224 bullet copper jackets, and can't tolerate much angular momentum before spinning apart.

Try loading down and you will be just fine.

I don't know if its possible to find the right balance of bullet integrity as it leaves the barrel, and bullet disintegration just as it hits the target. Would make for cleaning/gutting the animal to be a nasty proposition; too much meat damage. :D

voilsb
October 15, 2004, 10:37 PM
DMK said:
I've seen Army manuals that state 55gr. will work for practice and emergency, but it's not generally accurate enough to be issued with these twist rates.It's true that some manuals say to use 55gr only for emergencies ... and it has absolutely nothing to do with accuracy. It's point of aim vs. point of impact. 55gr ammo needs a different zero than 62gr ammo out of the same rifle. Therefore, if you're zeroed at 200yd with 62gr M855 ammo, you will not be zeroed for 55gr M193 ammo. You will still be able to get 4" groups at 200yd with 55gr ammo, it'll just be in a different spot than if you shot a 4" group w/ 62gr ammo.

GLOCKT
October 16, 2004, 07:48 PM
Most of your standard twist rates are 1:9
My Bushmaster shorty came with a 1:9 twist rate.Their 20" standard barrel is also a 1:9
It will accurately shoot as low as a 40gr round.
The 1:8 twist rate will take 70 gr and up.
I shoot 600 yard matches with a 24" V-match barrel 69 gr rounds and it to has a 1:9 twist.
It is suggested if I were to shoot the 1000 yard match move into a 1:8 twist,70 gr round.

Archie
October 16, 2004, 08:10 PM
It groups all the 50-55 grain bullets without much problem. It likes the 52 grain match kings (duh?)

It will not stabilize the 69 grain Sierra HPBT bullet. It will dramatically not stabilize them. Four foot (yeah, foot!) groups at 100 yards, keyholes at 25 yards. I mean they will just flat not stabilize.

However, the Speer 70 grain flat base round nose groups under an inch.

That is a difference in length of (heck, I can't remember!) not much.

Basic thing to remember is: A lot of overspin is better than just a little underspin.

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