WB
The old Lyman Cast Bullet Handbook always
Monday, November 29, 2021, 08:48

showed somewhat mediocre velocities using very fast powders. I always wondered why?! Dick Lee in his wonderful thick loading book published that most classic alloys gave out at around 25k psi. Not sure if that was gas check or not. But his point is you are fine below that point of alloy failure. Also accuracy seemed highest just below that point.

I have experimented and found I can get 50% higher velocities on naked cast gas check bullets using the slowest powders practical for the case capacity. In some cases rivaling factory jacketed speeds. Powder coating takes that to a new level. You basically have a "jacketed" bullet. It's a plastic poly jacket but enhances the alloy enough you get much greater speeds before failure.

Using slow powders I've had great success with .458 Win,.416 Rigby, .378 GNR, .338 Winchester, .25-35 Win. and .218 BEE. It is a delight that I can get factory speeds from cast bullets. As you are working, getting some type of expansion is the next hurdle. I've cold swaged HP into some bullets using the LEE sizer die as a tool to ensure concentric alignment. I just need to get back at it.