We have started to expand our section for subsonic load data here
We have also cross-checked our loads with those of other sources and came across two key topics:
Minimum Fill Rate
Other sources (i.e. Hodgdon) allow for very Fill Rates as low as 20%, i.e. only 20% of the available volume in a cartridge (after the bullet is seated) is filled with powder. To still ensure proper ignition, they need to assume the use of filler material. However, there are no comments in regards to that.
Minimum Powder Conversion
Our calculations show that some of the loads of other sources have a very low powder conversion, sometimes close to 50%, i.e. only 50% of the powder is burned when the bullet leaves the muzzle.
We are interested to get your views on the above. If you allow such values, you get load data for a large number of powders. If you restrict them, you get less. Please let us know what you think:
What is a minimum acceptable Fill Rate for Subsonic Loads?
at least 90%
at least 75%
at least 50%
at least 25%
What is the minimum acceptable Powder Conversion for Subsonic Loads?
At least 90%
At least 75%
At least 50%
At least 25%
Filler Material
Please comment on this blog and let us know when you use filler material, which filler material you use, and why?
I prefer Trail Boss or (much harder to find) Tin Star. I am not comfortable with adding my own fillers. I have found that Accu 1680 gives superior gas pressure with 300BLK to provide sufficient pressure to run the action. IMR4227, CFEBLK, and Lil'Gun frequently do not provide that needed pressure and the only thing that H110 consistently provides is enough flash to blind anyone unfortunate enough to operate low-quality night vision devices.
I started using Trail Boss powder for my .308, .300 rounds. It is a very bulky light powder. If I do use a filler, it is cotton.
You may also wish to note on the sub pages what secondary explosive effect is and how to avoid it through use of fillers.
I'd like to hear more on this as well, as Im just getting into working up sub-sonic loads for 9MM and 300BLK. Thank you.
I'd use Acrylic toy stuffing as it burns super fast and does not clog suppressors.