OK, not stellar, but progress all the same. Especially changing your hold!
My final comment on fillers, then I'll shut up:
I hang out (figuratively speaking), with the guys on the ASSRA website. In theory at least dedicated to the preservation of the 19th century Schuetzen game. The best of these guys can keep every shot on a salad plate at 200 yards, offhand, using iron sights. On the bench it's more like a silver dollar, AND they shoot for score, which means a tight group out in the 7-ring does you no good at all. The rules say plain base bullets. Everybody breech seats, rather than seating the bullet in the case. Cartridges vary from .25-20 Single Shot to .32-40, with a rare individual who can take the recoil of a .38-55 all day. (Many matches are 100 shots.) Top shooters do tend to use powders faster than 4198; AA#9, 4227, AA4100, etc. Case volume probably has something to do with it - the .32-40 is only 41 grains of water.
To the point: NOBODY today uses fillers. Some do use a tiny tuft of kapok or toilet tissue to keep the powder close to the primer, and it is very popular to use a thin wad of floral foam at the case mouth, just to avoid spilling powder. (Wads down on the powder cause chamber ringing!)
I'm a natural skeptic. Even the Gun Gods of my youth published some strange and even dangerous loads. Especially Elmer and his infamous "OKH duplex loads" scheme. Those were the days! No cheap electronic instrumentation, no computers, just load it up and tie a string to the trigger!
http://elmerkeithshoot.org/GA/1982_1...le_Charges.pdf Read this through - he has a little to say about fillers.
But then he also advocated a card wad down on the powder, which has now been proven to be THE prime cause of ringed chambers.
I cannot factor fillers into my QL models, so you're on your own in re: pressures. Do you have a chronograph? That'll give an indirect estimate.
Cheers!
Phil