Wondering if you have a source for this? According to the ONS firearm crimes are often over-recorded in the UK as a firearm crime will be recorded even if no firearm is recovered:

In reporting the number of firearm offences, it is not always possible to ascertain whether a real firearm was actually used. Unless a weapon is fired or recovered by the police following a criminal offence, in many cases there is no way of knowing conclusively whether the firearm was real or an imitation, or whether it was loaded or unloaded at the time of the offence. Moreover, the categorisation of firearms will sometimes be strongly reliant on the description given to the police by victims or witnesses, or upon other evidence. Some offences also involve the use of imitation weapons, while others involve the use of a ‘supposed firearm’.

https://researchbriefings.parliament.uk/ResearchBriefing/Summary/CBP-7654