Brian.
I quite agree, liners and excentric bushes are a good way to do it.
I was refering in my post to the notion of excentric one piece barrels, which on a lathe involve making a false centre for machineing. Not beyond the wit of man but a pain to do. And chambering is a problem unless it is done first as you have no true concentric surface left to revolve the barrel off of.

Regards