breechplug;my inline T/C's have 8 lands/grooves,most sabots have 4 petals,by indexing the sabot you can have all 8 lands in contact with the petals or only 4 in contact with the lands the other 4 lands riding in the slots between the petals(these load easier and can cause fliers,thou in my experiance not as bad what the op had)
and i would respectfully disagree that a clean barrel can't shoot accurately...........karl