By far the cheapest bullet to shoot just for practice is lead cast pistol bullets. The average cost for 100 is $25. BUT for some of us our inlines wont shoot them worth crap. Had a prohunter that the last owner was able to get one inch groups with cast. Tried them in my Triumph and it was 5 inch group. But if your gun could shoot lead cast that would be the cheapest. As for sabots most TC guns shoot the harvester crushed rib sabots really well. If you don't do cast I would try the XTPs. Not the XTP MAGS. Its way cheaper to shoot just the XTP.