RATE OF TWIST

What rate of twist will give me the best accuracy shooting 125 grain ballistic tips out of a 300 ultra mag. I'm cosidering building a species specific rifle.

The only one I have shot is in a 1-10".

Worked great.

Kevin; If, and this is a big IF, you will limit your bullet choices to those no longer than your 125 Ballistic Tip, you can do very well with a 1-14" twist. Regards, Eagleye.

Lots of information about this from various rifle barrel makers.

Lilja has software to determine the answer.
http://www.riflebarrels.com/products/software.htm

Sisk
.308 8" For bullets heavier than 220gr.
10" For bullets up to 220 gr.
12" For bullets up to 170 gr.
14"* For bullets up to 168 gr.
15"* For bullets up to 150 gr.

Pac-Nor
"a faster rate of twist may be required to stabilize these bullets. For example, a 12" twistbarrel will stabilize a heavier or longer bullet than will a 14" twistbarrel. Basically, the twist rate you choose should be sufficient to stabilize the longest and heaviest bullets you plan to use"
3 groove 6.50" 7" 7.50" 9" 10" 12" 13" 14" 15"
4 groove 10" 11"
5 groove 7" 8" 9" 10" 11" 12" 13" 14" 15" 17" 18"


What is the specific species you are tailoring this toward?

QuietHunter-

Great Links! :grin:

Thanks

Thanks for your reply, this would be a whitetail rifle.

whitetail with a 125NBT out of a 300RUM???? ARE U CRAZY????????? I sure hope you are loading that thing WAY down. For whitetail I would be thinking 150NAB. IF that 125 makes it out the barrel in one piece with full blown loads, you aint gonna have much deer left cause it gonna look like a bomb hit it. Cause I grant ya its gonna explode. It has been my findings that NBT are excellent at velocities around 2800 to 2900 fps. I know people drive them harder and have success doing it. But I'll stick with my NAB. When you can strike heavy bone at close range with velocities running in excess of 3200fps and get minimal meat damage and an exit wound it says a lot about a bullet. A NBT in that situation would have been explosive to say the least. That NAB was fired from a Borden 280AI to center shoulder impact on a whitetail @ +- 60 yds. So please use a little common sense in your bullet selection. If you planning on loading down to maybe 06 velocities, thats one thing. But if you goin full bore with that RUM...PLEASE RETHINK YOUR BULLET SELECTION.

I have to agree with Mr 7mm-06Ackley (280AI), rethink your combo. Consider using a 180 or 200gr pill.
The purpose of a Mag is to launch heavier slugs at the same velocity, not lighter ones at warp factor 8.