One other thought on this after posting....

When you first got the rifle and cleaned it before you took it to the range, did you use a bore brush and some quality solvents and scrub the bore? The reason I ask is sometimes the new rifles are packed with a thick protective grease that has to be scrubbed to removed.

You might want to take your rifle and using a bore brush and some good bore solvent, scrub the devil out of the rifle barrel. After that put a cleaning jag on and using clean patches run alcohol patches through the barrel until you are sure there is no gunk in there. Even the new rifles look clean will sometimes fool you. If you failed to get this stuff out, there could be a build up in the rifling and therefore once you shoot the rifle, the fowling is left much thicker in the barrel making loading harder.

You might also want to get some JB Bore Paste and scrub the bore with that stuff. It is an excellent cleaner and will knock all the little imperfections out of the barrel. The only other throught is you might have got an undersized bore. I sure this does happen and in this case all you could do is contact Thompson Center to fix the problem......