Right, ok . . . . . . my understanding of it is:
(and i am more than willing to stand corrected on this)
Firearms Certificate is required to possess a:
Rim Fire rifle (R/F) usually a cartridge that has no percussion cap in the centre, and is fired by the cartridge rim being pinched by the firing pin. There are various calibres are availabe.
Centre Fire rifle (C/F) rifle (again, various calibres are available, and the noticable difference is that with these cartridges, there is a little percussion cap in the centre of it - hence the name C/F
Tactical Shotgun [Correct?] - those