We have a question for the community. Hodgdon has recently published subsonic load data: https://hodgdonpowderco.com/wp-content/uploads/2023/04/subsonic-data-final-1.pdf
The list contains the following load data: .308 Win, 190 GR Hornady Sub-X, 2.69 C.O.L.: 2.690'' - 13 GR H322 Hodgdon
The bullet is 1.3'' long. Seated depth is then 0.63''. The empty case capacity is 56 GoW, the powder bulk density is 55.8 lbs/ft3.
So the fill rate (volume taken by powder in the cartridge) for this suggested load is around 33%. Only one third of the available cartridge is taken by the powder.
HOW CAN SUCH A LOAD ENSURE CONSISTENT IGNITION BY THE PRIMER? Has someone tested this load? Any feedback in general at what minimum fill rates you start to get problems /nervous?
https://www.xxlreloading.com/subsonic-load-data there is some sub sonic load data for the 8.6 BLK - may be that heps to answer your question. Tog et more filing rate i would have a look at:
Vihtavuori N32C Tin Star or ReloadSwiss RS 14] or Hodgdon TrailBoss