T/C XTP 240 grain accuracy issues

[samualh]

went out to shoot a new muzzleloader I bought from a farm auction almost by accident. A like new traditions lightning .50 full stainless for $100. I have a traditional Hawkins style muzzleloader but this is my first inline. Having bought the muzzleloader I went ahead and bought the boxes of T/C XTP 240 grain sabot bullets and only 6 were missing which I’m assuming are the only 6 shot through the rifle. I put a scope on the rifle and took it out today to sight it in and was having serious accuracy issues. I couldn’t hardly get the rifle to hit a 10” target at 60 yards. I then switched to the hornady boredriver 340 grain and then began to shoot about 2 moa which I’m more than happy with without working diffrent powder charges. Has anyone else had issues with these bullets? New to muzzleloading so any tips/info would be nice.