Trail Boss should have NO compression, period.

When I was working up loads for the 500S&W, the Hodgdon Tech told me to mark the case where the base of the bullet would end up and fill it up to there.

If I remember right, and memory is such a terrible thing to waste, it came to 16gr or so! That was in the 500 though so.................

If it were me, and there weren't any loads for the 41 and TB I would call. They are very helpful.

Personally, and I don't have a 41, I use Bullseye in my light target loads in 44Mag and have no qualms at all. They are 4.5gr under a 200gr LRNFP Cowboy Bullet. In the 41 case, that should be a good load too. Probably push it about 750fps to 800fps or so. Super light.

FWIW