Heavier bullets require a "faster" twist rate to stabilize the bullet. A 1:9 twist is pretty standard for bullets up to 69gr.
Actually I’m being a little rhetorical, here. My PSA stainless freedom barrel with a 1:7 twist is quite acceptable @1-1/2” groups. I just don’t like the long, hard, gritty trigger pull (unlike SgtBob and Ermey!)I just want a nice soft, liberal trigger pull like on my bolt action hunting rifles.