404 J Twist Rate

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Fastrig

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Starting to do my research for a 404J build. Would like your all's opinions on the twist rate for the barrel. The Montana Rifle Co. African lists their 404J with a 12 twist. Was thinking more along the lines of a 10 twist but have never had a big bore rifle, so maybe the 12 is more appropriate? Thanks for the input!
 
Mine wears a Pac Nor barrel. I believe twist rate is 1/14. It certainly is accurate.
 
Custom said:
Mine wears a Pac Nor barrel. I believe twist rate is 1/14. It certainly is accurate.
Click to expand...

Thank you...guess the 12 would probably be fine then. Thanks for helping with my "education" on big bore rifles, I'm a little lacking in knowledge in this area so it's greatly appreciated. Lots to consider and want to make sure the final rifle is as perfect as possible.
 
CZ Custom shop uses a 1-10
 
At a 100M

IMG_0992.JPG
 
Last edited by a moderator:
Fastrig said:
Thank you...guess the 12 would probably be fine then. Thanks for helping with my "education" on big bore rifles, I'm a little lacking in knowledge in this area so it's greatly appreciated. Lots to consider and want to make sure the final rifle is as perfect as possible.
Click to expand...
Fastrig, here is a link to a great book about every Big Bore caliber you ever want to know about..this book is available in the USA..maybe on Amazon or Safari Pres..
https://www.africahunting.com/threads/african-dangerous-game-cartridges-pierre-van-der-walt.6646/
https://pierrevanderwalt.com/product/african-dangerous-game-cartridges/

Read and study this book..there is none other this good...(y)(y)(y)
 

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1:14 for a 404 Jeffery is good twist for that gun. What kind of ammo do you plan to shoot through it ?
 
I presume you have the bullet choice sorted out/?? The next important issue you need to sort out is the type of action ....ZZK602 /or a magnum action is the way to go..(y)
 
Hoss Delgado said:
1:14 for a 404 Jeffery is good twist for that gun. What kind of ammo do you plan to shoot through it ?
Click to expand...

Was going to use DG factory rounds, believe they offer mostly 400 grain and 450 grain options. Hornady, Swift A Frame, and Norma all make what look to be good loads for the 404J. I'm not setup to do hand-loads, and just don't have the time right now to get into it, so it's going to be factory loads for the time being.
 
A little over a year ago, I ordered a 404 barrel from Krieger. This was for a Win M70 conversion project. Krieger did a 1-16 twist. The gun is accurate.

upload_2019-7-17_12-8-37.png


upload_2019-7-17_12-11-1.png
 
Gert Odendaal said:
Great, you will not have feeding problems..are you building yourself??
Click to expand...

No, I’m going to have our local gunsmith do the build...that way I know it will be done right...they will even spec out and do custom loads for me if I want them to and keep it all on file so I can reorder with a phone call. Really a great shop to work with.
 
Start with the bullets you want use.... Bullet diameter squared x 150, then divided by bullet length, equals twist rate in inches. That will get you get close to your optimum twist rate.
 
Mekaniks said:
Start with the bullets you want use.... Bullet diameter squared x 150, then divided by bullet length, equals twist rate in inches. That will get you get close to your optimum twist rate.
Click to expand...

Thank you very much.....love this site, you all are great!!
 
Gert Odendaal said:
Fastrig, here is a link to a great book about every Big Bore caliber you ever want to know about..this book is available in the USA..maybe on Amazon or Safari Pres..
https://www.africahunting.com/threads/african-dangerous-game-cartridges-pierre-van-der-walt.6646/
https://pierrevanderwalt.com/product/african-dangerous-game-cartridges/

Read and study this book..there is none other this good...(y)(y)(y)
Click to expand...

Amazon has the book but only in a Kindle version....folks online were saying the tables aren't readable because of Kindle's low screen resolution....was able to find the print version though at another place and going to order it. Thanks again!!
 
With a 404 Jeffery, you are most likely going to shoot either a 400 grain bullet or a 400 grain bullet. Velocity will be around 2300 FPS. For a Swift A Frame bullet and using the formula from @Mekaniks post (which I believe is known as the Greenhill Formula), I ran some numbers (hey, I'm an Engineer).

The number crunching suggests a 1-19 twist rate will work, a 1-16 is good and a 1-10 is probably more than you need.



upload_2019-7-17_16-6-40.png



TWIST RATE = (0.423^2 x 150) / 1.380 = 19.45


Running a 1-19.45 Twist Rate on the JBM Calculator

upload_2019-7-17_16-7-13.png

Output Data

Stability

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



Calculation using 1-16 Twist Rate

upload_2019-7-17_16-9-19.png




Calculation using 1-10 Twist Rate

upload_2019-7-17_16-9-31.png
 
Thaat's what I love about AH. Got a question, someone's got an answer and is more than happy to share it. I've learned so much here that I could never have found on my own. I'm amazed at the breadth of experience and knowledge available on so many subjects.
 
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