How light can you go in a trail boss sneeze/fart

[Jessegreenwood]

Hey, was thinking of loading some quiet plinking loads with pistol bullets in 303, considering getting a 100 grain lee mold, want it subsonic.
I have trail boss, but Hogden says don’t go below 75% fill, which I think would be a bit faster than my aim in 303, under 100 grains of lead.
Anyone know what the risk would be going down below a half case with trail boss? Incomplete burn, or could it detonate?
No shotgun powder to be had in Brandon, but could get something like Imr red from where I get the mold.
Just if trail boss would work, that would be great, already plan on a heavier one with trail boss under a 213 pill.
Crazy thoughts?

 

[Evanguy]

Not sure about trailboss but ive used 3 to 5 gr of tite group making light 303 cast loads. I got down to 700fps. Using 100gr .313

 

[Big bore dinosaur]

My gloss / mouse fart load is under 800fps.
Work down your ladder till the bullets sticks in the bore.
Tap out with a wood dowel.

I found they wouldn't stabilize and key hole in the target at slower speeds.