Shot it this weekend with 5744.
Loaded up with 24.0gr, 25.0gr, 26.0gr and 26.0gr.
I tried it with dacron filler.
24.0gr-- 50yds 1/2" to 1", 100yds 2" to 3". Blowback gone.
25.0gr-- 50yds 1" to 2", 100yds 2" to 3". Primers flat.
Didn't try the 26.0gr and 27.0gr loads.
I'm going to try without the filler next.