My general feeling is that most people will be fine with 55gr in a 1:8 twist.
That's a good assessment right there. Aside from thin skinned "blitz" type bullets spinning too fast to stay together or becoming unstable, bench rest type groups suffer from improper twist rate-bullet weight.
I had that problem several years ago while working up loads in a 22-250. Some tumbled, some simply disintegrated somewhere around 70 yards out.
A normal 55 gr. bullet shot out of your twist rate and rifle should be fine.
Barrel maker Shilen's recommendation of the best twist rates as far as accuracy is concerned in a .224 is as follows:
224 CF
- 7" for bullets heavier than 70gr.
- 8" for bullets heavier than 70gr.
- 8"* Ratchet rifled 4 groove
- 9" for bullets up to 70gr.
- 12: for bullets up to 63gr.
- 14" for bullets up to 55gr.
- 14"* Ratchet rifled 4 groove
- 15"* for bullets up to 55gr. driven 4,100 pfs or more
- 16:* for bullets up to 55gr. driven 4,300 fps or more