FWIW:
In 2 different 44mag's 7.0gr of trailboss and 3 different 180gr to 220gr bullets hold the x-ring (1 1/2") @25yds on an nra target.
I'm getting 3/4" to 1" 6-shot groups @25yds with 7.0gr of trailboss and a 200gr wc (top right).
On another website (castboolits.com) other members have reported the same results in their 44mag's. Namely 7.0gr of trailboss and xxx bullet.
7.gr would be a good place to start & while not in the 44spl pressure range. They are under 20,000psi and extremely soft shooting.