Remove thread protector cap on the 1/2"UNF silencer adapter thread, it just unscrews
This threaded adapter is Loctited into the end of the ally tube, you'll need heat & some way of grabbing on to it to unscrew it, really tricky to do without marking the finish. Do the same with the ally tube, heat & something clever to grab it, there's more delicate finish to worry about, holding onto the cone can be a challege, more finish to worry about.
This should leave the cone shaped end behind with a bare ally block in front of it, this is just a tight fit on the end of the barrel, pull it off with a little brute force. This leaves the cone shape free to just slide off, you say you have already removed the grub screw. If anyone is wondering where it is it is often buried under Loctite under the sling stud.
I had it easy, I'd already replaced the barrel on mine, which was anyway a well scabbled up barn gun so I didn't worry about the finish, I could just use Molegrips or pump pliers or something. The original barrel was effectively scrap, BSA was going through a bad patch & managed to put a choke at both ends, the accuracy was poor to say the least.
There is no packing in mine, which is an older model, about 2003-6 I think, it's not a silencer as such, more a cocking aid.