Thread: Lee 358-158-RF and Other Bullets

I'm guessing "neck tension" is what holds the bullet instead of a crimp.
Ap 70 is the equivalent of unique, pretty much the universal cast bullet powder. Fast burning powders will give you more consistent results I'm guessing there's a lot of unburnt powder in the bore with the other two as you aren't developing enough pressure for complete combustion.
Crimping may help but I'd look at trailboss first it's not designed for high velocities but it will burn clean