Have my eye on a new Kimber varmint model .223.

The twist rate is 9.

Is this pretty much standard for lighter grain bullets in this caliber? I will load nothing less than 40 grain nor heavier than 55 grain. Will be mostly punching holes in paper and will most likely use Sierra 52 grain match most of the time.

THANKS in advance and have a great Sunday.

"Bo"

To answer your question: no. To elaborate:

1:12" has been the standard twist for .223 for many years. It does well with upto 55 grain and some bigger bullets. The 60 gr Nosler Partition will usually stabilize in a 1:12" twist because it is very short.

Today, however, several manufacturers (Savage and Kimber come to mind) are putting 1:9" twist barrels on their .223s. It's still useable for the light bullets and will handle the 69/70 grainers. Tikka puts a 1:8" twist on its .223s, which will handle the 75/77 grain and maybe the 80 grain bullets.

If you only want to shoot ligher bullets then the 1:12" is fine, but the 1:9" gives you much more versatility.

The 1:9" twist should be just fine for the 52 gr Sierra you are contemplating using.

Does this answer your question?

LWD

one in 9 will also stabilize a lot of 75, 77 and 80 grain bullets...

they stabilize just fine in my one in 9 twist Savage also...

And the Faster Twist will increase your Pressure quicker - meaning you will be Over Pressure if you use a randomly picked Load near MAX that was Developed in a Slower Twist Barrel.

But, each Barrel is unique and you might reach the same Velocities as a Slow Twist. Just watch for a bit lower SAFE MAX than normal as you Develop your Loads.

It just caught me on a new rifle that had traditionally been 1-in-38" and they changed it to 1-in-20". What used to be Starting Loads with the Slower Twist are slightly beyond MAX in this new Twist.

Best of luck to you.

quote:

Originally posted by Hot Core:
And the Faster Twist will increase your Pressure quicker - meaning you will be Over Pressure if you use a randomly picked Load near MAX that was Developed in a Slower Twist Barrel.

But, each Barrel is unique and you might reach the same Velocities as a Slow Twist. Just watch for a bit lower SAFE MAX than normal as you Develop your Loads.

It just caught me on a new rifle that had traditionally been 1-in-38" and they changed it to 1-in-20". What used to be Starting Loads with the Slower Twist are slightly beyond MAX in this new Twist.

Best of luck to you.

Excellent point about pressure increasing quicker in a fast twist barrel. I'm currently working up loads for a new 223AI that has a fast twist barrel, and I got the surprise of my life when I had some primer cratering on loads that I thought were well below max....

Don

quote:

Originally posted by Hot Core:
And the Faster Twist will increase your Pressure quicker

At least theoretically this is true.....however I have not yet experienced this.....but must admit that my experience is limited to differences between 1-9" and 1-14" twists in the .223......and I understand some barrels are quite a bit faster than 1-9".

Theoretically one should be able to get higher velocities with a slower twist and I haven't experienced that as of yet! I've come to believe the energy that goes into rotation of the bullet is minimal however real it might be.

Further I've not encountered any reloading data that has warned to reduce loads for faster twists.

While I fully concurr with the above statement as a law of physics, it has not been a factor of consequence for me yet.

Possibly the 50 grain bullets I shoot in the .223 are not affected like the heavier bullets are.

I must also admit that I'm just too darn lazy to break out some old physics books to look up the formulas for rotary motion to see how many foot-pounds of energy actually go into rotation of the bullet.....any college students out there want to take this as a challenge?

Thanks a bundle, Fellers !!

For some reason, my "notifications" did not notify me that there were answers.
I just happened to check it anyway this morning.

Anyhow, these were the answers I was looking for. I am not interested in using bullets larger than 55 grain and was afraid that the 1/9 twist would not be best. It sounds like it will be OK for the smaller bullets, but maybe not perfect.

THANKS and y'all have a great week.

Bo

quote:

Originally posted by vapodog:
...Further I've not encountered any reloading data that has warned to reduce loads for faster twists....

Hey Vapo, It is not a "Warning" as such in the new Speer #14 on pages 690 & 691 concerning the 444Mar, just less Powder shown in their Loads. Note the Lab Notes on page 691 concerning the change in Twist Rate between the old version(which I had) and the new version(which I now have.

If you compare the IMR-4198 Loads shown for a 240gr Bullet, in Speer #14 with the old Hodgdon #26, the MAX Speer Load is the Starting Load in the old Hodgdon. I Verified the "new Speer" MAX Load is actually slightly above Factory PRE by shooting some and doing the Comparison measuring.

Had to Pull Bullets and Dump Powder because of it. If I'd started with my "old Loads", I would have been a bit more than 3.0gr too high.

Good Hunting and clean 1-shot Kills.

My .223, .223 AckImp, and 5.56mm barrels run the range of 1:7 to 1:12. I load differently for them and make obvious marks on the storage cases and ammo storage. 1:12 is safe for everything if you're just punching paper. 1:7 makes a noticeable difference with the heavy end of the projectile scale but 1:9 is a pretty fair compromise for "all of the above" ammo. 1:12 is reasonable and cheapest for paper and prairie doggies. Depends on what you want to do. The "animal that shall not be mentioned again" that HotCore and I argued over until we made friends again was taken with a 1:12 .223 Remington Chambered Shilen barrel on a custom bolt rifle with a 55 grainer and a scope and chamber matched dies likely worth more than the rifle.

My most recent purchases have been 1:9 and I think that's where I've permanently landed for future purchase and barrel making.

your only other concern should be then, that you for go using Hornady SPSX bullets and Sierra Blitz bullets ( not blitz kings)....

these bullets are fragile enought, that they will vaporize right out of the barrel of a 1 in 9 twist rifle... unless your MV is down around 22 Mag velocities...

Dakota based .22 Cheetah with a 1:12 barrel and soft cast bullets did a much better job of vaporizing anything than you'd ever imagine nor have suggested. Didn't make a 20 yard target.

tom`

Speaking of twist rates...

Have any of you guys thought about the difference in lethality of a bullet spinning faster, ie. higher RPM. I have noticed a huge difference in my faster twist .223s using the same bullets. I had never really thought much about it until I started using the Barnes TSX. It holds together so the faster you spin it the more tissue damage it does. I would imagine with a frangible type like a ballistic tip the explosion difference would be awesome on varmints.

Perry

who has done a study on twist rates and lethality? In larger calibers I doubt that it has much impact on terminal performance. I could see a lightweight 22 caliber bullet going to pieces faster if two orthogonal forces are being applied to it at the same time, thus any given bullet would be given to fragment more readily at a higher spin rate. Taken to the extreme the bullet will fragment in mid air on the way to the target. I did not know that Tikka made a 1-8 twisted gun, that is the danger of these forums, you find out things that result in money being spent!

Jimmy
My buddy just got the Tikka and it shoots very well!

Perry