1 in 9" is more common these days, but the 1 in 8" twist lets you push heavier bullets that perform better on bigger varmints like coyotes, and buck the wind better for longer range shooting. I can't think of the last time I pushed a 40grn pill out of a .223, I typically opt for a 50-55grn for hunting, but I keep a good supply of 77grn Matchking's around to feed my 1:7.7" Kreiger barreled AR-15 when I want to reach out and punch paper WAY down town.