One thing I haven't seen mentioned here yet is the relationship between velocity and twist. Frankly, any bullet will stabilize in any rate of twist if pushed fast enough, but there's only so much powder you can cram into a .223 case and a point at which the bullet will go poof (the magical grey mist).
The other thing not mentioned is that barrel length does have an effect on this mess as well...to a degree. The shorter the barrel, the less time the bullet is being forced to spin by the rifling. So, what will stabilize in a 20" barrel may not always stabilize in a 16" barrel of the same twist rate unless you up the velocity to compensate. You can also go too long on a barrel to the point that all the powder is burnt prior to the bullet leaving the muzzle. When this happens, typically you will see velocity drop and pressure go way up as any remaining barrel length is just holding all that pressure in with no additional energy (powder) to propel the bullet, thus resulting in drag.
The rule of thumb for twist is to be fast rather than risk not being fast enough. Typically you would be looking at 1:10 or 1:12 twist barrel for the bullet weight specified (50-60gr) from a 22"+ barrel. Considering the 16" barrel length provides less velocity and less rotational force applied to the bullet, a faster twist is mandated to stabilize the same weight bullets being pushed at the same velocity.
This being the case, I'd definitely go with a 1:8 twist....especially if you'll be shooting factory loads.