Is 1:9 Twist too fast for 165s? Shooting terribly

[Eurodriver]

I’ve got a new 300 WSM with a ARC action and 1:9 proof barrel. I’ve shot Barnes, Federal with two different bullets and a few others all in 165gr. They’ve all shot terribly. Think 3-4” groups at 100y.

I’m going to hand load, but wondering why they’d all be grouping so poorly. Is 1:9 “too fast” for 165? I have 200gr Terminal Ascent on the way and then should have enough federal brass to do some testing but just wondering if this is typical. I’ve never seen a match rifle do so poorly.

Thoughts?

 

[ShtrRdy]

Have you found any ammo that shoots well in it? Maybe there is something else wrong?

 

[Eurodriver]

Have you found any ammo that shoots well in it? Maybe there is something else wrong?

Nothing I’ve shot so far in 165 shoots under 3 MOA.

 

[Lost_Phil]

I would make a modified case or buy one and see what the distance is to the lands, as it sounds like you might have more free bore then you think, and the shorter bullets do not like it.

But I still would follow the course you are planning and see if hand loads will work out better.

 

[Terry Cross]

The twist rate is not a culprit.
I have a bunch of 300PRCs and short barrel. 308 Win. out there with 1-8.5" twists. Some have played with bullets as light as 155gr and no issues.

 

[Ledzep]

The twist rate is not a culprit.
I have a bunch of 300PRCs and short barrel. 308 Win. out there with 1-8.5" twists. Some have played with bullets as light as 155gr and no issues.

Agreed. You can trend dispersion a little worse with faster twist rates (eccentric mass spun faster) which is often countered by stability related issues among other things the same way or opposite way.... Moral of the story it's usually much bigger differences barrel to barrel than twist rate to twist rate (assuming SG > 1.2).

Edit: OP, try different powders if you're hand loading.

 

[Eurodriver]

200gr Terminal Ascent - Must just not like the lighter bullets?

 

[45-90]

Nothing wrong with 1-9 twist for 165 gr, as far as accuracy goes, vs twist rate.
I've shot down to 125 and 130 gr bullets in my 1-8 and 1-9 308s with good accuracy.
For factory rds, change ammo.
Handloading, you can adjust "things" to improve accuracy.

 

[TheOE800]

Shot 168gr 308win in 1:8 half inch groups at 100. Same with 215gr 300prc.