Well sorry, but to me posterity has absolutely nothing to do with it. And unlike you I feel an honest question deserves an honest answer.
Any commercial caster SASS or otherwise offer 2 choices
1. 8-12 BNH for velocities under 1K
2. 15-22 BNH for velocities up to 1400 fps.
That’s their parameters, no in between.
Most so called HC for 357 have all been between choice 2 with 18 being the norm. Meister, Magnus, lasercast or MBC and others that are no longer around. Missouri Bullet has all the options including coated, good product and really good folks to deal with.
Now, carry on for posterity and feel safe and secure knowing that anyone that wades through this thread, the question was at least answered.
