.223 rifle twist: fact vs fiction

[flashhole]

To some, this may not look like all that good a target. The intent was NOT to put all the bullets through the same hole. At the local range we engage in some friendly competitions. Everyone puts money in the kitty. Everyone shoots at the same size target at 100 yards. First shot has to be cleanly in the 10 ring to continue shooting or you're out. You shoot at your own target in progressive rounds. You must have a clean hit on your target without cutting the edge of your target or hitting an existing bullet hole to proceed to the next round. Your target gets smaller with each shot. This was a winning target. I like the Sierra 63 grain bullet with my Kimber Longmaster Classic 1:9 twist barrel.

 

[Jim Watson]

So you are shooting for the smallest NON "one ragged hole" group. Cute.

 

[flashhole]

No, were shooting for the money, a NON "one ragged hole" with all shots completely on target and not touching is what it takes to win it.

 

[lysanderxiii]

Use a .17 caliber rifle, it will improve your chances of winning....

 

[sirgilligan]

The group on the right is a perfect example of a twist that's a bit too slow. NOTICE, the bullets ARE NOT tumbling, they just don't group well. This is why I think to myself "BS" when someone says 62 gr. lead core bullets tumble out of their 1-12" twist or 75's tumble out of their 1-9".
A buddy of mine coaches our 4H High Power team and told me some of the kids rifles with 1-9" twist will stabilize the Hornady 75 gr. HP, but not the A-Max.

35W

I have no idea if the bullets were lead core or not. But the Browning with 1:12 was key-holing, bouncing them off the ground and skipping them, etc. He was shooting from a bag with the target on a box sitting on the ground. He was trying to sight it in and at first he thought it was just shooting low, se he kept changing his scope trying to get on paper. When he finally landed one on paper it was a key hole, and all the rest after that.

I don't BS. I may have my facts wrong and I will email my cousin and ask. I am only human.

 

[sirgilligan]

So, I emailed my cousin, he is busy in DC right now but took time to respond briefly. He said anything over 55 grain wouldn't group better than 3". He didn't comment on what the particular 62 grain was that was key-holing, so I don't know if it was M855 or not, but I don't think it was because I don't think he would have shot M855 through a .223 Rem chambered brand new Browning.

p.s. He responded with some more info. He tried several bullets above 55 grain and even some hand loads and he did say he did try M855 as well.

 

[mshootnit]

data point: I have a 22" Ruger m77 bought new in 1994. This rifle features 1/12 twist I believe. It will accurately shoot 60 gr. Partitions.

 

[200Apples]

flashole

This was a winning target. I like the Sierra 63 grain bullet with my Kimber Longmaster Classic 1:9 twist barrel.

Nice! Sounds like fun.

Curious, how long is that barrel?

Thx.

 

[adcoch1]

Flashhole, I am curious about that barrel length too...

Sent from my LGLS740 using Tapatalk

 

[Nature Boy]

Not being snide, just the way it is.

MacIVshooter,

What's your point?

 

[jmorris]

First shot has to be cleanly in the 10 ring to continue shooting or you're out. You shoot at your own target in progressive rounds. You must have a clean hit on your target without cutting the edge of your target or hitting an existing bullet hole to proceed to the next round. Your target gets smaller with each shot.

That's is an interesting game. I have played with trying to get the longest bullet tear through the same axis of a target before.



A business card was kind of the "standard" but when you cut them in half that's just half a card...

 

[Bart B.]

Best thing to calculate stability for bullets is:

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Use this site to get bullet length for what you want to get stabilization data for:

http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/

There's quite a range of muzzle velocity and twist rate that'll shoot sub MOA at short ranges (up to 300 yards) for a given bullet. Note the faster a given bullet is spun as it leaves the muzzle, the more those not perfectly balanced will jump in some direction off the bore axis. Which is why benchrest folks add a tenth grain or two to their charges when shooting in cold weather; their warm weather load spins bullets barely fast enough to keep them spinning true and fly straight.

I've shot 190-gr. 30 caliber bullets leaving 2550 fps from 1:12 twist barrels that shoot sub MOA at 1000 just as easy than if shot 3100 fps from a 1:12 twist barrel. Both show up as "green" stability in the JBM Ballistics' Stabilization program above. 22 caliber bullets are no different.

If your bullet and its muzzle velocity computes to a "green" stability factor yet won't shoot well at short range, the problem's not that bullet's data. Maybe they're a bad lot of bullets or they're unbalanced by reloading (crimping them in case mouths?) or slammed too hard into the rifling by the wrong powder used. Could be less than ideal rifle, ammo or shooter.

 

[Laphroaig]

Here's 2 more data points that I've found while shooting mid-range F-class at 500 yds.:

My 20", 1:9 Savage 10PC in .223 will stabilize 77 gr. SMK's but not 80 gr. SMK's.

However, another shooter with a Savage varmit rifle, 26" barrel, 1:9 twist did stabilize 80 SMK's. I think his loads might have been hotter than mine and the extra 6" of barrel must have spun them fast enough.

Laphroaig

 

[adcoch1]

Here's 2 more data points that I've found while shooting mid-range F-class at 500 yds.:

My 20", 1:9 Savage 10PC in .223 will stabilize 77 gr. SMK's but not 80 gr. SMK's.

However, another shooter with a Savage varmit rifle, 26" barrel, 1:9 twist did stabilize 80 SMK's. I think his loads might have been hotter than mine and the extra 6" of barrel must have spun them fast enough.

Laphroaig

This is good information to have, as is the ballistic calculator in a previous post. Getting a good idea of why certain things work so well and others that sound good don't... it is really amazing how much misinformation is out there about 223, thanks for all the input.

Sent from my LGLS740 using Tapatalk

 

[lysanderxiii]

Best thing to calculate stability for bullets is:

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Use this site to get bullet length for what you want to get stabilization data for:

http://www.accurateshooter.com/ballistics/bullet-database-with-2900-projectiles/

There's quite a range of muzzle velocity and twist rate that'll shoot sub MOA at short ranges (up to 300 yards) for a given bullet. Note the faster a given bullet is spun as it leaves the muzzle, the more those not perfectly balanced will jump in some direction off the bore axis. Which is why benchrest folks add a tenth grain or two to their charges when shooting in cold weather; their warm weather load spins bullets barely fast enough to keep them spinning true and fly straight.

I've shot 190-gr. 30 caliber bullets leaving 2550 fps from 1:12 twist barrels that shoot sub MOA at 1000 just as easy than if shot 3100 fps from a 1:12 twist barrel. Both show up as "green" stability in the JBM Ballistics' Stabilization program above. 22 caliber bullets are no different.

If your bullet and its muzzle velocity computes to a "green" stability factor yet won't shoot well at short range, the problem's not that bullet's data. Maybe they're a bad lot of bullets or they're unbalanced by reloading (crimping them in case mouths?) or slammed too hard into the rifling by the wrong powder used. Could be less than ideal rifle, ammo or shooter.

Just a few things to add...

First, as good a calculator as that is it is just an approximation. If you put in the information for an M193, 55 grain bullet (.755" long) out of a 1-14 twist, 20" barrel (3300 fps approx.), it tells you that it will be unstable. They aren't. At least until the temperature drops to around freezing.

Which brings us to two, the temperature and density play a part in bullet stability, a bullet that is stable on a hot day, may keyhole in the winter. Depends on how close the stability factor is to unity.

And three, yellow is still stable. A 55 grain, M193 FMJ has a out of a 1-12 twist, 20" barrel has a stability factor of just over 1.25, a solid yellow. So as stated above, if you are green, you should never have a problem.

Lastly, that calculator (all of them, in fact) are biased to the conservative side. The shape of the ogive and boat-tail determine the location of the center of pressure and center of gravity. Therefore, upon these two numbers depends the over-turning moment. The over-turning moment is what is needed to calculate the exact spin required to achieve static stability. Two bullets of the same length and weight, but differing in ogive and boat-tail dimension will have slightly different stability factors for the same twist and velocity.

The calculator works because the density of bullet material and the ogives that work well cause the CP and CG to be close to the same point for a given length. Some of these calculators start to fail if you try to use bullets that are not copper jacketed, lead core bullets.

 

[Bart B.]

Good stuff, lysanderxiii. I'll add a little icing on that good cake you baked.

Bullets a thousand yards down range are moving about half as fast and spinning about 20% less as when they left the muzzle. But their twist rate is typically twice what it was when it left the barrel.

For example, Sierra 30 caliber 175 HPMK leaving 2667 fps from a 1:12 twist barrel spinning 160,000 rpm with a JBM Sg of 1.503 is moving 1194 fps at a thousand but spinning about 131,000 rpm and twisting 1:6.5 inches now with an Sg of 4.078. See post #7 in:

http://www.thehighroad.org/showthread.php?t=810965

 

[Doc7]

I would think RPM matters more than inches traveled per revolution...depends on your definition of rate I guess.

 

[WVRJ]

I have 2 .223's with 1 in 9,and 1 with 1 in 12.The 1 in 12 will stabilize 64 gr Nosler flatnose bonded bullets,but anything longer than that is a no go.Even 60 gr ballistic tips won't shoot well.The two with 1 in 9 rates will shoot most anything under 75 grains.but I've found them both to like 69 grain bullets.The bolt gun will put 5 69 gr TMK's in the .2's and 3's at 100,and I've shot a few groups under 3 inches at 600 yards on a calm day.For me,the 69's are about the limit of the 223's real world capacity.But lost of guys seem to like heavier bullets and those will need a 1 in 8 or faster.It's all about what you want to do.

 

[MachIVshooter]

I would think RPM matters more than inches traveled per revolution...depends on your definition of rate I guess.

You can't really separate the two. Bullet length and bullet velocity are what determines necessary RPM, and required RPM and velocity are what decides the twist rate.

 

[greyghost01]

I had a handi rifle in 1-12 twist, It just never shot above 55 grn bullets well at all, I called the factory and was told it was designed to shoot the 45 grn bullet some would shoot the 55 grn but not recommended for anything heavier, So I sold it as they said they offered no barrels for a 1-9 or 1-7 twist, I do not save hides so I'm not worried about small holes so it just did not work for me

 

[flashhole]

"Flashhole, I am curious about that barrel length too..."

Barrel length on the Kimber Longmaster Classic in 223 is 24"