Most interesting. I normally shoot M193-type ammo in my ARs, and I long wondered about whether their 1-7 twist was too rapid for those light 55 grain bullets. These are the same bullets that were adequately stabilized in Vietnam-era M16s and their 1-12 twist rate.
My concern was never about accuracy, though. If they were wildly inaccurate from a 1-7 barrel I probably would have noticed that. My concern was if an overly stabilized projectile would tend to drill through a target (ice pick wounds) rather than the yawing and tumbling that improves lethality. The M193 in Vietnam was known to be devastating against unarmored enemy personnel, and a lot of that was attributed to its relatively slow 1-12 twist.
For better or worse though, 1-7 is the military standard for over 30 years now. You would think ammo makers would optimize their bullets for that twist rate. I am probably going to start trying more of the 69-77 grain ammo.