Is a Grenade launcher a Section 1 Firearm Component ?

[Seaspriter]

projecting a stabilised missile

Far be it for me to comment on UK Law (other than Old English Common Law), but the term "stabilized missile" generally refers to an object with fin stabilizers. Please correct me if I'm wrong, but the No.1 cup grenade launcher (I have one) was designed to propel an unstabilized grenade that was also hand-launched. My 1950s Energa grenade launcher on the No.4 MII is a different animal, as the Energa was a Rocket propelled missile grenade with integral fin stabilizers.

The U.S. M-1 Grenade Launchers held a hybrid fin-stabilizer that clipped on the bottom of a pineapple grenade, making it a stabilized missile.