From published data 6.0 grs of Power Pistol or Hodgdon Longshot will
yield over 1,000 fps out of a 4" barrel with a 158 gr cast SWC. My own
tests do the same with 5.1 grs of 231. These are +P loads and stay
within +P limits. If you choose 158 gr JHPs for +P loads you have to
realize that you are not likely to get much if any expansion at 1,000
fps.