I only need to look at the homicide rate in the UK and compare it to that in the US. It's four times higher in the US.
I think that says it all.
When even British criminals and mental patients could own guns, their homicide rate was lower
And we are not the British. We are a highly diverse society with demographic groups whose homicide rates vary from less than one per hundred thousand to at times over three-hundred per hundred thousand.
If you want to adopt UK policy, wouldn't it make more sense to adopt the policies they had in place when their murder rate was far lower? Take 1960, for example, when criminals could have guns, before they tried to eliminate them, there were only a fourth as many British homicides per year as they had in 2003. The declining trend since then seems to come purely from reductions in the amount of domestic violence.
And of course, without guns European murder rates have been twenty to fifty times higher. The culture changed, even while weapons became far more lethal.