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?
Hi - we got some direct feedback by mail, thanks for that. The current punchline is that people would accept fill rates of only 50% when a filler is used. We have updated our subsonic load data accordingly and accept fill rates with a minimum of 40% and flagg these loads that a filler is recommended. We leave this post open in case there is more feedback.
Minimum fill would be anything that will cycle the round without adjusting your gas block on a semiautomatic (AR type) rifle. Using powder like Trail Boss will nearly fill the case without using filler.
I would recommend using IMR/Hodgdon data from:
https://hodgdonreloading.com/rldc/
Less confusing and reliable. The best powder is Trail Boss
I've used grits or cotton before as a filler, but there maybe something out there that is better ?
Hi - just checking if anyone has a view? What is the minimum fill rate you are accepting for normal and for subsonic loads?!