My friend has one of these Thompson Center rifles. He tells me that when he cleans it, it has some sort of section at the bottom of the barrel that is about .22 in diameter. He says he has to use a .22 brush on a rod to clean that section. What the heck is he talking about. Were these barrels made different than others. Does it serve a purpose. Could he possibly have something lodged in there that has a hole through it, and not know it. Can someone please explain this to me. Im dumbfounded and I try to keep up on my muzzleloading data.