My two HANDI 223s are 1 in 12 and seem to like the ULTRAMAX 52gr BTHPs.
I get 1' to 1.5" at a 100yds.
My friend has a 1 in 9 and his won't shoot anything but hand loads with either 60 or 62 grainers, I'm not sure which.
He was very disappointed with it being a 1 in 9.
No one told him when he bought it that the factory had changed the twist rates of the 223s.
It's starting to shoot better, about 3/4" to 1" at 100yds.
With factory's the best it would do was 2.5" to 3".
He was not a happy camper.
He just picked up a BC 45-70 that won't shoot anything lighter that 405gr lead.
300gr WIN. HPs barely stay under 6" at 100.
The 405s do about 1.5" to 2". Not to bad.
We both like the 300gr HPs the best.
Both my BC and my HANDI 45-70 will stay under 2" at 100 with the 300 grainers.
I don't know why the factory wanted to mess around with the twist rates of calibers that showed time and time again that they just fine with the twist rates they had.
Who knows?
Getting back to your 1 in 9 twist 223, I would say try several of the heavier bullet loads from about any of the ammo makers. You should find one your gun likes.
Lets hope so!
Good luck and keep us informed with your progress.
LONGTOM