Twist for 6mm-223 ?

[Tozguy]

I am planning to rebarrel a 223 to 6mm for .243 bullets in the 65gr to 75 gr weight range (like the Hornady 75 Vmax for example). The barrel would be 24 '' long. Does anyone have a recommendation for what twist rate to use?

 

[Terry]

Try this...

http://www.bergerbullets.com/products/varmint-bullets/

 

[Tozguy]

Terry,

I had already used another twist calculator but it was good to use Berger's site also. Thanks for the link. It is rather difficult for me to predict muzzle velocity so it would still be good to hear from anyone who has some experience to share.

 

[butchlambert]

You didn't give much info. What will the new cartridge going to be? With what little you have given us, 12 twist.

 

[rcw3]

+1 on the 12" twist recommendation - - no real advantage to be gained going looser with that cartridge. Better to err on a little tighter than too loose.

Robert

 

[Roe]

I went with 1:10 in mine. Shot mainly 70 Nosler BT, 85 Sierra GK and 87 Hornady HPBT.
Used powder Vit N130 and shot 70 to appr 950 msec, 87 to 834msec 24" barrel. Numbers from memory.

 

[Tozguy]

The cartridge is simply going to be a 223 case necked up to 6mm. Varget would be the first powder on my list of candidates. The 12th edition of 'Cartridges of the World' shows some loading data for a 70,75 and 80 grain HP bullet but none for Varget. There are no specs for the barrel used but the book provides some velocity numbers in the 2800 to 2900 fps range. The gun would be used only for informal target shooting.
Butch, please let me know if I forgot something. Much appreciate all the comments so far but any additional info would be welcome. Thanks everybody.

12 twist going once.......

 

[jscandale]

If I were building this rifle, I would go with 1:10.
Is it a bolt gun or gas gun?

JS

 

[Tozguy]

Bolt gun, 24'' barrel.

 

[swd]

I went with 1-10" on my 6x45. Shoots up to 85gr for a little more versatility. Try Hodgdon BLC(2), you'll be very happy.

 

[MarkS]

Tozguy,

14 tw would work, but the 75Vmax is on the edge in some 14. I like the 12tw best for my 6BR's. you can run a 87vmax in the 12.

Mark Schronce

 

[butchlambert]

Listen to Mark.

 

[louielouie]

Also know as the 6x45, some loading data can be found at http://reloadersnest.com/frontpage.asp?CaliberID=300. Here they're showing just under 3000fps for a 75gr boolit.

 

[Tozguy]

It looks like we have narrowed it down to 10 or 12 twist.
I'm thinking why not one of each

 

[Old Navy]

Is that not a 6 TCU? Later! Frank

 

[treeman]

if I'm not mistaken the 6mm TCU has a 40' shoulder the 6mm-223 has a 23' shoulder

 

[treeman]

p.s. if some one has a tc barrel and will chime in I would go with the twist tc uses and I would guess 10 twist

 

[Tozguy]

Cartridges of the World, 12th edition, states that all the TCU cartridges are necked up 223 cartridges with no mention of a change in shoulder angle. This book does show a slightly shorter case length of 1.74'' for the 6 TCU versus 1.76'' for the 6mm223. Twist for the 6 TCU is 12 versus 10 to 12 for the 6mm233. Interestingly, Redding lists different die part numbers for each of these cartridges.

 

[firearmdoc1]

6mm TCU has the shoulder pushed forward and is 40 degree angle. 6mm-223 has shoulder in same location as 223.