There are about 4 times as many people in USA than Britain 30,000/19 = 1598, Sixteen hundred times the number of gun related Murders....

I moved to Toronto in 1989. There wer 32 Murders in Toronto that year. Something like 1,500 murders in Detroit (a smaller city) that same year. Admittedly a bad year for Detroit but America is certianly the G8 champ for violent crime. whether it is per capita or by gross numbers.

It's a gunslinger mentality, having the weapon in hand make one more likely to act. The possibility of the other guy having a weapon increases the fear and possibly makes one more likely to shoot.