A follow up ....
I forgot to mention that she had a few boxes of Federal Match .308 155gr which is no longer manufactured or sold.
Using the same rifle, range and wind conditions, she fired lots of that ammunition at the same 4 foot target at 1,000 meters (1,100 yards approx) and her groups were consistently less than 12".
However, perhaps more germane to this discussion was the fact NONE of the 50+ rounds of 155gr she fired "key holed" like the 168gr Federal ammo did. All were clean well defined holes and apparently remained stable right to the target.
BTW, just for clarity of authenticity, the instructors sitting in the chair and heard in the backgrpound are Keith Cunnigham and Linda Miller (click here), who coach and take the Canadianteam to Bisley.
Regards,
Badger