Charon, when you pull the nose a tad further away from the porridge, you might actually see the plate.
USA = 3/4 of homicides performed with a gun, mostly handguns.
UK = 1/4 of USA homicides. Murders with firearms of my stats page: 62 against 8.259 (Population comparison is roughly 1 to 5 so those 62 would be 500, so 500 against 8259).
rough figures, but look at
http://www.nationmaster.comSo, the brickwall answers. I think you CAN NOT claim that European crime rate will go down with a better access to deadly and conceilable arms. Europe as a whole, and even the UK is more densely populated than the USA, and very mixed as well. European population is also larger than the US. Note that I assume that Europe and the USA are the closest to compare. Streetgangs are everywhere, problem is that yours are and have always been (notably in the famous time of the Chicago typewriter

) much better armed. Getting a gun in the USA is no problem at all for any idiot. Getting a gun in Europe is a different issue, harder, and more expensive.
So, since the Euros, - or Brits, - do much less of shooting each other, as well as killing each other and robbing each other etc as the US do, - with noticably more difficulty in aquiring arms, - how on earth do you expect anybody to belive that increased free-floating arsenals will improve it further?
Still a wall.....