I have successfully loaded N320 with the 147 FN \”Heavy Match\” RMR bullet for subsonic loads to use with a suppressor. N320 is supposed to burn clean and best of all it is 100% burned according to Quickload calculations. I am trying to reduce the amount of filth that a suppressor inherently drives back into the firearm.
Specifically I charge with 3.5 grain of N320 and seat the bullet to a COAL of 1.110 inch. That bullet is 0.625 inches long so if you use the round nose, just measure it and seat the bullet to that difference plus the 1.110 to get a COAL that yields the same case seating depth, hence about the same pressure. My load yields 902fps muzzle velocity in a Sig P226 with a 4.4 inch barrel, as measured with a Labradar unit . The load cycles well in all my firearms tested with or without the suppressor and includes a Ruger PC 9mm with 16 inch barrel.