if I had to get Id say 12 grains is a better starting point. So long as you are not compressing the powder you should be fine with trailboss.
Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull.
all 23 of my guns are 45/70 govt 357 mag, 22 or 12 ga... I believe in keeping it simple