Northern Constabulary used to take the relaxed view that one FAC sufficed until about ten or twelve years ago. Then they became far stricter, partly as the result of the Dunblane shootings. Thereafter they tightened up on shotguns as well. Up here the ATCOs no longer get to play with verys and bird scarers, it's all done by the firemen. Many moons ago when I had the good fortune to work for a regime that was jointly run by both Britain and France; the pistols were supplied by one colonial power and the ammo by the other. Calibres of inch and a half and 38mm come to mind. Fortunately for our safety, the cartridges were marginally bigger than the pistol bore so we couldn't use them. This was far from the worst example of Gilbertian farce involved in the whole performance.