Real world experience, Hart 1:14 in .222, the 53 Vmax was not even close to stable. Went back to my Speer TNT and the the bullets Dusty recommended above, in the vein of 52 HP, and stellar results returned.
Now, every 55 PSP I've ever tried has shot fantastic. Even quality FMJs shot well. But the 53 Vmax was a no-go.
Now, every 55 PSP I've ever tried has shot fantastic. Even quality FMJs shot well. But the 53 Vmax was a no-go.