“Some of the pistol cartridges that I reload which are powerful enough to kill a horse, take only a couple of grains of powder, “
YOU reload .22’s?
No, I have never reloaded a .22 cartridge. I do not know anyone who does. The smallest caliber that I reload for pistols are .30 caliber. I also do not cast any bullets smaller than .30 caliber. Do you understand the difference between rimfire and centerfire cartridges?
My favorite powder for pistol cartridges is Hodgdon Titegroup, there are many full power pistol cartridge recipes that take only a couple grains of Titegroup and a projectile in the 90 grain range. A typical projectile in a .22 cartridge is in the 40 grain range or less.