Not sure what in my post you are disagreeing with. A Court would definitely accept that, for example, an illegally re-activated bolt-action .303 SMLE rifle is a licensable section 1 firearm and give you 5 years imprisonment for unlicensed possession of it.
However, how could any UK Court decide that a catapult is a firearm? Section 57 (1) of the
Firearms Act 1968 states that a firearm is 'a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged'. Your Preston Shooters linked text states that the definition of a "lethal weapon" is 'a weapon capable of firing a projectile with sufficient force to inflict more than a trivial injury i.e. with sufficient force to puncture skin'.
Surely, the key in this context is the word "barrelled". Catapults, slingshots, crossbows, longbows, compound bows and recurve bows don't have a barrel and so even if they are classified as a "lethal weapon" they can never legally be defined as a firearm.
"Lethal weapons" are not automatically illegal in the UK. The Offensive Weapons Acts banned some of them, like flick knives, balisongs etc, but catapults, slingshots and bows were never mentioned in them. Recently, they have also banned curve-bladed swords (including katanas), knuckle dusters, combat style knives, zombie knives etc, unless they are antiques.
