That's the problem. The copper in the Thor/Barnes is very stiff.
When you get the sizing kit to see which size fits your bore before ordering the regular Thors you'll get one size that goes down perfect. The next size up can't even get started and it's only .001 bigger.
It's not like fitting lead bullets. Copper is unforgiving.
The CVA crown likes Powerbelts and sabots that are easy to start. Bullets like Thor and FPB can be a bear to get started.