oneounceload
Moderator
I have had to scrape the fouling out of my Brileys with an exacto knife before.
That sounds like you don't clean them very often or you are using some recycled plastic wad. I use Brileys, and the worst buildup I have ever had took about 600 rounds to get some started - but a spray with brake cleaner and a bronze brush and they were clean in about 5 seconds.
If you like Mullers, buy them and use them. IMO, the best chokes are the fixed ones in a Perazzi or Superposed barrel.......