Too slow a twist with produce an unstable bullet and poor accuracy.
Too fast a twist is detrimental to accuracy.
A 1:9" or 1:10" twist will stabilize all common bullets less than 64 grains in weight, without degrading accuracy. Faster twists and heavier bullets in the .223 Rem / 5.56mm are a solution to a problem that doesn't exist. If you need longer range or better terminal performance, use a rifle chambered for a larger cartridge.
shooting 80 gr Sierras is an option that is available and has applications. 600 yd slow fire prone is one. I have fired my spacegun with these bullets at 1000 yds and the rifle/bullet combo performed well. The barrel is 26 inch SS with 1:7.75. At 1000 yds all my rounds were still supersonic.