As I understand it, if you order a spare gun barrel for a project, it occupies a "slot" of the relevant calibre on a S1 FAC cert. Qn1: Is that right? If one wanted to self-build a double rifle, You'd presuambly need 3x slots on an FAC: Slot 1 = Barrel Blank A Slot 2 = Barrel Blank B Slot 3 = The finished double-barreled gun once assembled and proofed. (Let's assume the person in question is a private individual doing a shed-project, rather than an RFD) Qn2: What process do you have to go through when a barrel blank (or more than one) gets assembled with other non licensed parts into a complete Firearm? Qn3: I've always fancied Harper's "Seven Barreled Volley Gun" off Sharpe. How many barrels of legal (non-pistol) length can you cobble together before the Plod tell you to stop taking the urine and slap a Sect-5 status on the project, as it's essentially a machine gun? I daresay it'd make a difference if it had a different trigger for every barrel, rather than one thet set them all off simutaneously!