I will suggest, from experience that the 38-72 is overbore
capacity. I had loaded it with  72-78 gr Swiss 1.5 
with a 380 grain bullet. Of course my Krieger barrel has a
10 twist, so I can use such heavy, long bullets.
What twist is your barrel?
I recall that I used around 22 gr 4759 and Lyman 335 gr bullet to fireform 405 hornady brass after having sized it in the 38-72 die. Then, I neck turned the brass since I have a Dan T tight neck Match reamer that was used to chamber the barrel. 
I can say that my experience with my more recent 38-50 Rem Hep was almost instant fine shooting success as compared to
the experience with the 38-72
beltfed/arnie