Re: .223 varmint bullet, 1-9 twist, will it fail?
Just in case anyone reads this in the future (like I just did,) or the OP is still looking for information, I thought I'd add a few lines.
I've had in .223 Rem., a 1/10" Savage bolt gun 10+ yrs ago and presently own a 1/9" Remington. Bottom line? Shoot whatever bullet you want to in it and you'll be fine. The Savage didn't quite stabilize the 75gr AMAX's back then but did great with 69 smk's Everything up to that weight shot great also.
My current 1/9" has shot 80gr Nosler CC's just to see if it could- I had them laying around because I have a 1/7" gas gun- and it did. 69's and 75/77's shoot just fine but it's purpose is being a coyote gun so it shoots 53 VMAX's on the regular with 40, 50, 55, and 60gr VMAX, BlitzKings, TNT's, and Ballistic Tip also. Nothing has come apart or shot poorly. When I say they shoot "fine" I am meaning -1/2" MOA out to 300 yds.
Bottom line, I've seen a little velocity loss over a 1/12" or 1/14" twist with all other things being equal, but don't worry about spinning bullets apart or over stabilizing them in a 1/9" twist.
Just a side note/question- I think Capt? wrote that an animal will walk away from a .50 bullet if not hit properly? That's incorrect. Out of a muzzleloader, maybe, but a center fire .50 BMG will drop an animal shot just about anywhere above the knees and elbows.