I'm not so sure that you are seeing tumbling because the profiles aren't quite right for tumbling round nose bullets of that weight -- the holes are too long for their width.
What is the quality of target paper you're using. Sometimes you'll get tearing of the paper with the very low velocities I think you've got. I get those tears when I use ordinary printer paper to make my targets (.38 Special, 40 S&W, .44 & .45). The hole quality improves when the printer paper gets smacked at higher velocities.
I still can't rule tumbling out at this point.
Many of the commercial lead bullets are very hard -- with the need to have near max pressures to get good obturation and eliminate the gas cutting. Per Hodgdon's web page (
http://data.hodgdon.com/cartridge_load.asp), you can increase the pressure a bit more by going up by a few tenths of a grain. Increasing the pressure adds velocity and might improve the appearance of the holes.
If you try that or other corrective measures, pleas let us know waht worked and what didn't for you.
PS Totalda said it very succinctly while I typed this long-winded note!