What is being seen is that velocity is used to increase the RPM when the twist rate is not tight enough. Get that bullet spinning fast enough and it'll eventually stabilize. Downside is the effect that max loads tend to take on a barrel over time, especially in fast movers like 22-250, Swifts, .243, .25-06, etc. Spin some bullets--typically thin jacketed varmint bullets--too fast though and they fly apart in flight.
