I suspect the "exact" 1-14 twist affects how well the 60-grain Partitions stabilize. Twist will vary slightly in barrels, except (usually) for hammer-forged barrels. The 60 Partition is right on the margin for stability in a 14 twist, and any little thing will cause problems, such as the twist actually being, say, 1-14.3.
In my last Swift, a tang-safety Ruger 77, it wouldn't shoot consistently unless I took the rifle up to about 7000 feet up in the mountains. Even at 4000 feet on a warm summer day, in a 5-shot group 2-3 would land close together, and the others would scatter, sometimes into 3" or more. This was in a rifle that would put five 55-grain Sierra hollow-points into 1/2" or so.
I finally quit trying to get them to shoot consistently in supposed 14 twists, because too often it was a waste of bullets, powder, primers and time. They're much more consistent in a 1-12 barrel, the standard .223 twist, and often shoot really well in a 1-9 or 1-8.
There's another advantage in "over-stabilizing" them: BC is higher. They ain't the sleekest bullet anyway, so I'll take any edge possible.
