For sizing those bullets try to find one of the Lee 7/8x14 dies in 356 or maybe 357..what ever is appropriate for your guns. Looking at the velocitiees you were getting it looked like when you got to about 4 to 4.1 gr you were reaching point of no return with that gun/barrel length. a different powder may be in order or a longer bbl. I found many years ago that unless a bullet was made specifically for the way it was going to be used HPing it or even flatteniing the point didn't seem to do much for making them expand. There was at one time a bullet mold that cast a hard base and a very soft point that were then either glued together of heated somewhat to make 'em into one bullet. I had some and it seemed to work ok but it was made for the 44(in the one I had). More work than it was worth.. I have a thing you put 22 LR into and file the ends flat and with that soft lead bullet it does work very well on garden raiding wabbits...maybe something like that would work for you...Maybe 180 gr soft 38 bullets with the m sized and then filed on the end down to your weight range. Lot of work but maybe possible