when you said you shot off your open hand, there is an alternative try shooting off the top of your fist, rest your fist on the table/bench etc and rest the rifle on top , you can use your thumb for lateral support and often a glove is beneficial!
by doing this you reduce considerably the muzzle flip caused by the rifle bouncing off any solid rest, you must also ensure the butt or bottom of the pistol grip is not in contact with anything!

we have an L shaped shooting bench at our range so that your right elbow is supported too, using this bench and shooting off the top of my fist I can get a sub 30mm five shot group with my HW98 at 102yds , provided that is the wind cooperates!