As Ron told you, that BP is most definitely 1/8 channeled. We aren't talking about the flash hole itself. There is a difference. Pictured here
I'm not 100% sure on this, but every TC breech plug I have experienced (209 primer types) have a 1/8 flash channel. With 60-70 shots through it, even if only 20% of those shots were with BH, that flash channel is probably crusted up pretty hard. Like Ron said, start with something smaller and end up with the 1/8. But do NOT use a motor (Dangit Ron not all are machinists) Ron works on and modifies breech plugs a lot and gets a bit carried away in his advise sometimes without considering the mechanical knowledge of some may not be on par with his own
Just use good sharp bits
BY HAND and it will eventually clean up. Soak the Breech Plug in some good solvent over night. That will help loosen things up.
Edit to add: And whoever told you Powerjunks wern't a good option for Elk was NOT misleading you. Hell they aren't a good option for whitetail! Some paper shooters like them because they are definitely accurate out of a lot of rifles but their terminal performance is "lacking" to put it nicely. To put it honestly they suck wind!