Funny, I have had the same result in my 7x 57 Ackley improved. It's an awesome load. Moves a 150 Gr. Ballistic tip, out to around 2900 FPS, using a moderate load and is most accurate in the middle range of the load chart.
H-4831 works better for me with the 168 Gr. and dip charging at the bench though.
I’ve pretty much settled on the 150 gr myself.
Anything under 150 can make a pretty good mess on the exit side.