Agreed.  A 1X9 barrel should have no difficulty with 69 grain bullets.  In fact, the 1x9 twist rate owes it existence and popularity largely to the appearance of the 69 gr. OTM bullet in competition.  Generally speaking, most any 1X9 twist barrel should stabilize anything up to and including 73 grain bullets, with particularly good barrels stabilizing up to 75 grain.

But, as for the root of the original question, there is much greater resistance (friction) to the forward motion than there is to the rotational motion of the projectile.  And then there is gravity.  For all reasonably practical cases, the bullet will either transition to subsonic or hit the ground long before gyroscopic forces (or lack thereof) would become a problem.

Fair.  Most of what I've read says 69 gr is the max reliable weight, but some stabilize higher.  Fine, but my larger point was that for any given bullet weight, you have to have sufficient spin by virtue of velocity and twist to get the initial stability.  Once you get it, will it generally stay stable until it goes subsonic, when all bets may be off?  Put another way, I'd like to know if I'm stable and consistent and accurate at 100 yards is that also an indicator that I'm going to stay that way thereafter until subsonic.  

From the other reply, it sounds like having the right twist is mostly about getting that initial stability in the first 10 feet and, if you do, you're probably o.k.  That would have been my guess, but is why I asked.

This is relevant to making ammo decisions about my ARs, which are both 1/9 and 1/7, but more important for my 22-250.  It's 1/14.  I know from testing it will stabilize 55 gr pills at 100, even 60gr Partitions.  Not all do, but mine does if they are hot.  Lower than 55 gr is no bueno in my book for deer, even though they are small hill country whitetail.  Knowing that 55 gr is really pushing it for a 1/14 22-250, I was curious about the downrange performance as I work up loads.  I don't want something that looks good at 100 but destabilizes at 200.  Yes, I shoot targets at longer ranges and can check this myself and will as I work up more loads, but before I do I was curious about the feedback.  With all the ammo experts around here, and the relevance to ammo generally, I posted here instead of the reloading forum.