"Firearm", within the definition of the Firearms Acts, means a lethal barrelled weapon of any description, from which any shot, bullet or other missile can be discharged. It includes any prohibited weapon, whether it is such a lethal weapon as aforesaid or not, and any component part of such a weapon, and any accessory to such weapon designed or adapted to diminish the noise or flash caused by the firing of the weapon.
Firearm, within the terms of what you are allowed to hold on a firearm certificate, would obviously not include any prohibited weapons. Neither would it include "shotguns", as they are held on a shotgun certificate. Except, that is, for Section 1 shotguns, which can only be held on a firearm certificate.
A Section 1 shotgun differs from a conventional shotgun, by virtue of the fact that it has a magazine capable of holding more than two cartridges. These are known as "pump-action" or "semi-automatic" shotguns, where cartridges from the magazine are loaded by hand "pumping" the action, or by the discharge of the previous round. These weapons are required to be held on a firearm certificate.
This is too large a subject to describe here. It has its own section, Prohibited Weapons, where greater detail is available.
Well, if you take away Section 2 shotguns, which are held on a shotgun certificate, and also eliminate prohibited weapons, you can have any other weapon you want. Provided you can supply a "good reason".
Most applicants require small or full bore rifles for target shooting, as a member of a Home Office approved club. Others request muzzle-loading hand guns for the same reason. Others still, use rifles for vermin control or deer stalking. Provided good reason is satisfied, all these weapons can
be legally held on a firearm certificate.