The first thing you need to do is ditch the Bore Butter. If you need to swab with BH209 you need to use another product like Hoppes #9 cut 50/50 with 91% rubbing alcohol. I can load some crazy tight sabots without ever swabbing when shooting BH209. Super Glides are one of the smallest loaded OD sabot ive seen. So yes its possible you have one of the crazy tight T/C barrels. The red 3 petal sabots that come with the Hornady SSTs might load easier for you.
First question that needs to be asked is....Did you scrub the snot out of the new barrel before shooting it?
2nd?....What did you use to lube the bore after cleaning it?....Please dont say you used Bore Butter.
BH209 is a nitro based propellant (nitrate ester) and you should be using common centerfire solvents and lubricants with it.
The most common solution for tight T/C bores is a jar of JB Bore Cleaner and some Kroil. This might take 100+ passes and several patches to see an improvement.