I owned one of the older Huntsman guns with knock-out breech plug, acquired in trade sometime after 1981. I do not recall having to take the barrel off to remove the breech plug. The radiologist I cited as a source of the report of a breech plug in the head was the best shooter in our club, and an amazingly talented gunsmith, making beautiful reproductions of everything from a Jaeger to a classic Kentucky rifle. He was a quiet, serious guy, and I had no reason to doubt that he had indeed seen this in a radiology journal.
The Huntsman was safe enough for one shot, but repeated firing caused the fouling problems I described: frozen firing pin, with failure to fire or firing on closure; interference with lockup, allowing the gun to pop open upon firing. It was OK for one shot, such as in hunting, but dangerous at a shooting match. I sold it for $25 to a guy who wanted a muzzleloader for hunting, after warning him of its problems.
I DO NOT appreciate the sneering tone of some of the postings. I'm not some ignorant twit who doesn't know the difference between lead balls and matzoh balls. I was attempting to pass on information about a VERY SERIOUS safety problem I PERSONALLY experienced. If later Huntsman rifles are safe, that's very good. However, I never heard of a recall on the older model, and there are likely a number of them still in circulation, capable of killing at BOTH ends.