I took a Mk1 barrel to the machine shop to press the taper pin out using a short dumpy tool. Just the smallest tweak and the pin almosr fell out. Such that I'm sure a hammer would have doe the same. The sleeve shouldn't be a press fit onto the barrel, it was a ground, tight but running fit and they knock off quite easily. After all, they were originally made to be able to be screwed on and off for a few threads and locked in place by the........... anyway.....

Incidentally Elvis, the reason why the sleeve was a 'stainless' material was that it could be removed, to put a blank firing sleeve in place for training etc etc. In short, support the larger diameter pin side of the barrel and hit the taper pin xxxxxxg hard with a xxxxxxg heavy hammer using a larger diameter punch, slightly recessed so that it won't slip off the pin. The pins are a normal eaasily obtainable general engineering taper pin.

PS I've got some of your records!