You CAN'T OWN A GUN in the UK
Not without lots of paperwork and tons of evidence you really really need it.
Has it stopped crime? Absolutely not. Illegal guns exist. Knives and other blades, and blunt instruments became the easier weapon to obtain, and they're doing MORE crime because of it... you see, the police aren't physically two feet away from everybody so it takes time for them to get there, Time in which you could be dead or severely injured.
Do your research, discover the statistics that prove where guns are not outlawed, crime, especially violent crime is less than areas where nobody can legally own a gun.