Rather than use stillsons which distort the ferrule and can make it oval and therefore grip even harder into the barrel I prefer to mig weld in (put in loads of heat) an old spark plug and whilst it is still nice and hot use a big adjustable or socket to remove the ferrule. I’ve also removed them by mig welding on a piece of flat bar. Just be careful on old barrels on large bore sizes as one day the cylinder top will come off with the ferrule……
Cheers
Richard
