So far as I know, the only legal way to dispose of one that's on FAC is to hand it in for destruction.

I shall have to do that with my Brocock Pietta Navy Colt sometime before I croak to avoid leaving the missus in possession of a Section 5.

When possessed as air weapons prior to the 2005 act, they can be held on FAC by the original owner, as I believe without a Good Reason requirement, and they can be used in any situation where it would be legal to use and air weapon.

As it happens, the Navy Colt would be especially difficult to convert to a live shooter, because there's no recoil plate to contain firearms pressures at casehead and primer, and it would require some very fancy engineering to make and insert one. Some say that criminals don't care how dangerous their weapons are to fire, but I think most would want to protect face and eyesight.

On all Brococks I've seen, the lineup of cylinder chambers and barrel, never especially precise in the first place, has been further compromised by the clearance fit of cartridge nose in the forward part of the chamber, resulting in considerable asymmetric shaving of the .22 pellet and poor accuracy. A couple of thou misalignment counts for more in a small calibre than in the original size, and I've never seen one of these revolvers capable of better than a 1" - 1.5" group at 6 or 8 yards.

They'd've been more of a loss to airgunning if they'd been better made.