Trail Boss was developed for Cowboy Action Shooting, using "soft" lead bullets. When I first started loading sub sonic for my suppressed .44, Trail boss was recommended to me. I found I really could not get enough of it in a .44 case to propel a jacketed 300 gr bullet. Worked great with lead semi-wadcutters of 240 grs. With those at about 850 - 900 fps, it really is quieter than my pellet gun, although probably not a lot more lethal. After confirming Trail Boss was meant for lead only, I used Universal, then Tight Group for my sub sonic loads, and both work well with either hard cast of jacketed bullets.
Mike
Heavy'ish .308 caliber bullets and Trail Boss are pretty much the universal recipe for subsonic loads in the .308 Winchester.
I've run mine to 300 and they stay minute of beer can.
Travis
