What twist to use?

[coyotejosh]

I am currently in the process of getting ready to build a 308 only question I have is I will be shooting 168 or 175 SMK. So the question is what would be an idea twist. Will be using a Krieger tube 20 inches heavy contour. Manners stock 700 action.

 

[rscott5028]

12 would be on the edge of what you've stated depending on elevation, bullet, etc...

11 would definitely do the job

10 would allow you to shoot virtually any 30 cal bullets

Benchresters tend to stay right on the edge. But, for general purpose, it's better to be too fast than too slow.

-- richard

 

[elkaholic]

12 would be on the edge of what you've stated depending on elevation, bullet, etc...

11 would definitely do the job

10 would allow you to shoot virtually any 30 cal bullets

Benchresters tend to stay right on the edge. But, for general purpose, it's better to be too fast than too slow.

-- richard

Agree with Richard. If you know for sure that you will NEVER want to shoot longer bullets, go with the 12 twist........Rich

 

[coyotejosh]

Thanks fellows I will have to go with the 11 seems to fit the manner that I am going to use it

 

[Joe King]

Speaking for personal experience. Pick the twist that will stabilize the longest heaviest bullets you think you'll ever shoot and go one step faster. I had 2 different rifles rebarreled. My 7mag I have always really liked heavy for caliber hunting bullets, and never figured I'd want to shoot vld bullets, so I got a 1 in 10 twist. Now I'm shooting vld bullets and 175gr and heavier vlds won't stabilize (or shouldn't) 1 in 9 and I would have been good. Did the same thing with my 22-250, and being stuck with 55gr or lighter the only exception is my riffle stabilizes a 53gr vmax when it shouldn't. One faster on both rifles would have opened a lot more options.

 

[Bart B]

When those 22" barreled M14NM's and M1A's were popular for service rifles in competition their 1"12 twist barrels did great with bullet weights from 168 through 180 grains. Some folks used 1:11 twist barrels for those bullet weights but accuracy equaled what the 1:12 ones produced. I suppose if the weather and powder temperature was pretty cold, the lower muzzle velocity produced in a 22 inch barrel would be better for accuracy with the 1:11 twist.

The above aside, none of the above equalled the accuracy produced with 7.62 NATO chambered Garands using Sierra 190's in their 1:12 twist 24 inch barrels.

A 20 inch barrel's going to get lower muzzle velocities with the same peak pressure compared to a 22 inch one with the same load, chamber, bore and groove dimensions. So, as mentioned by others, a 1:11 will do well. Except for 168's past 700 to 800 yards; if they're Sierra's, they probably will slow down to subsonic speeds at that point and change direction a bit.

The US Army's Advanced Marksmanship Unit Team set a service rifle team record at this year's Nationals using AR10's with 20 inch barrels shooting Berger 185's:

http://bulletin.accurateshooter.com...set-1k-records-at-interservice-championships/

I've no idea what load was used, but the military rifle teams have a long history of using handloads close to blue pill (proof load) pressures.