Since I found that CBA shooters haven't made any substantial improvement in rifle accuracy in over 20 years, I've been experimenting and reading about jacketed bullet and rimfire shooting, looking for a secret.
My experience with a chronograph and both jacketed and cast bullets suggests that MV variation does NOT correspond to accuracy variation, at least at 100 yards.
The rimfire community DOES seem to agree that MV variation DOES correspond to accuracy variation at 100 yards; and take actions to reduce that variation by, for example, weighing/sorting cartridges.
It occurred to me that MV variation could be reduced with an adjustable, spring-loaded, pressure relief valve; a barrel pressure manager.
A hole drilled in front of the chamber and threaded, a needle valve, and a spring loaded adjustable force arrangement are easily imagined and easily constructed.
Perhaps MV / pressure variation by the shooter is A way to improve cast bullet accuracy.
I have a Savage .22 barrel as the test bed, who will volunteer to do the machine work?