Yes the military quickly went to a 62 grain ball ammunition requiring a faster twist than a 1:12. Who knows for sure what bullet that they intended the .22-250 to be used with it had been wild catted for several years before it was commercialized. It was very popular for pushing sub 50 grain bullets past 4000 fps.
Well I believe the military used the 55 gr bullet through the Vietnam war, and I believe up to 1984. There was less use for longer range shooting like there is in desert warfare. I believe that is when a heaver bullet and faster twist was put in place.
As for the 22 250, I now recollect the 50 gr was the original bullet weight as it was for the swift. It was the 4000 fps barrier, and that's the reason for the slower 1 in 14" twist.