Nitrox - The UK is not good for handguns (or any guns really) but there is a concession

Certain cartridges are considered "obsolete" and guns chambered for them are not classed as firearms
(unless you have live ammunition with them in which case go straight to jail)

This includes all pinfire, bores larger than 10, and most rimfire (except .22 and a couple of others)

Many of the older big game cartridges also but not nitro military calibres

They made a mistake with some of the pistol cartridges, with the criminal gang element buying handloaded .44 Russian, .32 and some metrics, so we had to put those on a collector's certificate or dispose of them

I have .577 Snider, .577/450 MH and a .500 on certificate but woe betide me if I get caught shooting the handguns with that ammunition

TH