afaik the firearms act does not include an exemption for antique ammuntion thus a licnece or certificate is required this would consequently effect the restrictions under CEMA on importation, placing them as a restricted item and unless a valid licence is presented liable to forfeiture.
CPS advice on antique firearms;
Section 58(2) of the 1968 Act exempts from the provisions of the Act - including certificate controls under sections 1 and 2 and prohibition under section 5 - all antique firearms which are sold, transferred, purchased, acquired or possessed as curiosities or ornaments. The word "antique" is not defined in the Act but Home Office guidance on the subject can be summarised briefly as follows:
If modern ready made ammunition can be bought and fired using the weapon it cannot be classed as an antique;
A muzzle loading firearm is antique;
A breech loading firearm using a rim-fire cartridge exceeding .23 (but not 9mm) is antique;
A breech loading firearm using an ignition system other than rim-fire or centre is antique;
A breech loading centre fire firearm originally chambered for cartridges which are now obsolete and retains that original chambering is antique.
However, each case should be dealt with on its merits and advice on individual weapons should be sought from the FSP. The case of R v Burke 67 Cr App R 220 dictates that it is for the Prosecution to prove that the firearm does not come within the ambit of section 58(2) and it is a matter for the jury to decide upon.
and open source research indicates;
Section 58(2) of the Firearms Act 1968 provides that an antique firearm which is possessed as a “curiosity or ornament” is no longer subject to the provisions of the Act. This piece of legislation forms the basis for the free possession of antique firearms. The concept of not needing a licence for an old gun is well established and stems from the Pistols Act 1903.
The antique exemption does not extend to ammunition. Collectors of bulleted cartridges –
irrespective of their age or ignition system – require police authority to possess them.
Paragraph 8.5 note (i) of The Home Office’s Firearms Law: Guidance to the Police states
“the exemption does not apply to ammunition, and the possession of live ammunition suitable for use with an otherwise antique firearm may indicate that the firearm is not possessed as a curio or ornament.” This is a sweeping statement which is routinely used as the justification for prosecution in cases where it is alleged that an antique firearm was not possessed as a curiosity or an ornament