I have use Trail Boss in my J frame snub nose with a 148gr HBwc
with the swaged soft Speer #4618 bullet from 1.15" out to 1.20"

Lowest charge of 2.4grs did 560fps but was not as accurate as
2.7 grs at 672 with a f209 primer.

I have loaded 3.4c in my M686 but it did not do as well for a "Full Load" in a 38 special
as a full load of Bullseye or w231 for accuracy with heavy recoil.

It also works well with a 158 Lwc in my revolvers.
Stay safe.