I've never had good results with .30 cal sabots. They need a fast powder, like 4227, RL 7, to really work right, and that seems to get them moving too fast.
Accuracy was never there, but they didn't keyhole, either. This was with 68 gr. Hornady BTHPs in an M1A.
I have made them work successfully in my Marlin 1895 using Hornady muzzleloader sabots and Trail Boss powder.
Velocity was only around 1600 fps or so, though, which is why I believe that the .30 cals are being oversped.