I own buckets and buckets of used pipes and if they were well used, the odds are previous owners formed a cake, which was the universal advice of the pipe makers for maybe a century, and may still be.
I have all kinds of reamers and I gave up on them years ago.
A reamer has no conscience. It will remove cake and briar all alike.
It takes a little practice, but the rounded “flesh blade” of a cheap pocket knife held at 90 degrees makes a perfect scraper to take off all the cake down to bare briar.
After the carbon cake is all gone, I keep it gone by frequent use of a twisted paper towel soaked in Everclear.
If you smoke outside in the wind, cake protects some against burn out. And for a novice the cake sort of filters and softens the smoke and I like lots of nicotine and hearty flavors, now my tongue is like a piece of leather.
But cake stops the taste of the fine briar you paid for and it slows down the natural coloring process of a fine briar pipe.
I’ve found a slight, black, oily film in the chamber is the best. Just barely enough cake to say there’s a trace.