Best Twist rate for a 404 Jeffery

[Shootist43]

After reading in a recent post that 450 Gr. bullets were better Buff medicine than the old tried and true 400 Gr I started to worry. The heavier bullet requires a 1/14 twist rate to stabilize it. Apparently there is some support for the thought that the "normal" twist rate for the 404 is 1/16. I was wondering if the 404 I recently purchased would stabilize the heavier bullet. I contacted one of the CZ Custom shops and was told that the twist rate in the barrels they install is 1/10. Now I'm concerned that it might be too fast for one or both of the bullet weights. Does anyone out there have any experience with a 1/10 twist rate barrel in a 404 Jeffery using 400 or 450 Gr. bullets?

What kind of group do you get at 50, 75 or 100 yards? What distance do you have your 404(s) sighted in at? How many of you are running optics instead of iron sights?

 

[Mekaniks]

Do you handload? If so, take one of your bullets and measure it. Or look up the bullet dimensions in a reloading catalog.

The formula for optimum twist rate is this-

Bullet diameter squared, times 150. That total is then divided by the bullet length, equals the twist rate.

 

[Ray B]

I don't have direct experience with the twist rates in 404s, however in a similar area, I asked a tech at Sierra regarding shooting 55 grain 224 bullets in a 1-7 twist 5.56. that twist is designed for long target bullets of at least 75 grains. the standard twist for 55 grainers is 1 - 12 or 1-14. I was concerned about over-spinning the bullets. The tech said that over spinning a bullet at normal velocities is very rarely a problem, particularly compared to under spinning them. As to 450 grain bullets in a 404, I think the length is only slightly longer than the 400s, so a twist that works well with one, should do well with the other.

 

[375 Ruger Fan]

The bullet length, weight and velocity all factor into the calculation.

Woodleigh bullet data:
http://www.woodleighbullets.com.au/bullet-lists/traditional/405-458-list

450 gr = 1.491" long

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

Stability
The Miller stability value. It should be between 1.3 and 2.0 to ensure stabilty (the military uses 1.5).

Re ran for a 14 twist rate

 

[Shootist43]

I'm a bit confused by the results of the Miller stability value results for both bullet weights. If the optimal stability value is between 1.3 and 2.0 (military uses 1.5) what do the stability values of 6.128 and or 3.127 signify? On the other hand if the minimum stability value is 1.3 to 2.0 then the values shown indicate a very stable bullet.

 

[Shootist43]

I don't have direct experience with the twist rates in 404s, however in a similar area, I asked a tech at Sierra regarding shooting 55 grain 224 bullets in a 1-7 twist 5.56. that twist is designed for long target bullets of at least 75 grains. the standard twist for 55 grainers is 1 - 12 or 1-14. I was concerned about over-spinning the bullets. The tech said that over spinning a bullet at normal velocities is very rarely a problem, particularly compared to under spinning them. As to 450 grain bullets in a 404, I think the length is only slightly longer than the 400s, so a twist that works well with one, should do well with the other.

I too have a number of black rifles in 223 caliber with varying twist rates. For my rifle with 1-7 twist I was advised to shoot a minimum 62 Gr. bullet. Supposedly the faster twist rate would "spin the jackets off" 55 Gr. bullets resulting in a loss of accuracy. That problem however may have been because of the design of the 55 Gr bullet. I have friends that compete in U.S. National Matches that require the use of "Service Rifles." The bullets they use in rifles with a 1- 7 twist rate are the
75 Gr you mentioned and often heavier. Knowing this is what prompted my question in the first place. The "key" may be in the Sierra Tech's choice of words i.e. "normal velocity." I'm not sure exactly what that means.

 

[Shootist43]

The bullet length, weight and velocity all factor into the calculation.

Woodleigh bullet data:
http://www.woodleighbullets.com.au/bullet-lists/traditional/405-458-list

450 gr = 1.491" long

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

View attachment 197308


Stability
The Miller stability value. It should be between 1.3 and 2.0 to ensure stabilty (the military uses 1.5).

Re ran for a 14 twist rate

View attachment 197309

I was not aware of the JBM Ballistics calculator. Thanks for sharing.

I's still looking for the clarification requested in my previous post regarding the values of the stability significantly exceeding 1.3 - 2.

 

[CAustin]

Art a 400 grain bullet will be plenty of good medicine for buff.

 

[375 Ruger Fan]

This is an excerpt from an article on Realguns.com: http://www.realguns.com/articles/200.htm

A twist rate is an indication of a means to an end. Bullets need sufficient rotational speed to stabilize, with rotational speed coming from a combination of twist rate and bullet velocity. A bullet, based on a good deal of empirical range data and analyzing tons of handload performance, needs to rotate near or above the 190,000 revolutions per second rate for optimal stabilization and good accuracy. Moving closer to and above 300,000 rpm tends to expose imperfections in a bullet's manufacturer with diminished accuracy and velocity as the symptoms.

The formula for finding RPM is:

So, with a 1-10" twist and 2100 FPS, RPM = 2100 x (12/10) x 60 = 151,200 rpm.

So this less than the ideal range (according to this article) of 190,000 to 300,000.

Using the 1-14", you get an even lower rpm, 108,000.

So it seems the JBM calculator and the formula here is giving different answers.

 

[Shootist43]

375 Ruger Fan, I couldn't agree more. CZ claims that "most" African PHs use their rifles, I was hoping to get a reply from one that uses a 404 Jeffery, and or a reply from an AH member that uses one. The owner and head smith at Triple River Gunsmithing told me that they put a 1-10 twist barrel into all of their CZ Custom Rifles regardless of caliber for whatever that is worth.

 

[Rob404]

My CZ550 in 404Jeff with a 1-10 twist rate at 100 meters using 84gs of Win 760 pushing a 400g Swift,Velocity was 2363fps this was the first time out with the new rifle. I could probably improve the groups but it's good for now

 

[Shootist43]

Thanks Rob 404. Out of curiosity was that with a scope or Iron sights? If with optics what make and power? Whose rings and bases are you using? What range do you intend to have the gun sighted in at for hunting?

 

[Rob404]

Thanks Rob 404. Out of curiosity was that with a scope or Iron sights? If with optics what make and power? Whose rings and bases are you using? What range do you intend to have the gun sighted in at for hunting?

I use a Leupold VX3 1.5x5 (these had a 100.00 rebate) so the price was right the bases are Alaska Arms, I think a 100 yds will do the trick. I haven't tried the 3leaf open sight yet but being they are far enough down the barrel I get a clean look so I'm thinking it would work just fine

 

[DWB]

Stop stressing ang shoot your gun!!! The 450gr conventional bullets work just fine!

 

[DWB]

For those who hasn't seen a comparison: