Thanks for the reminder on the size, Taylor, I recall now - about the 'large' sizing by Rayle to allow the use of a .250" rod. Tks for the measure on the Hoyt barrel, ERH. Have you measured the rate of twist?
Dave, I suspect one might have to use a caplock to allow the use 4f as a main charge in a .25. While it might blow powder up into the nipple when shoving the ball down, it might not be enough to slow ignition? I'd merely use 3F and be happy.
Both my .32 and .40 have 48" twists and they don't foul at all. I only shoot 35gr. to 40gr. 3F in the .32, but the .40 gets 653F to 75gr. 2f depending on circumstances, yet neither build up fouling with water based or the oil based lubes I use.