That has to be the stupidest thing you have ever said. And you mostly only ever say stupid shit.
If you aren't willing to make the comparison on a per capata basis , how do you make it make sense?
The experience of Norway is that the determined killer can get what he wants for a weapon , if he has to cross national borders , this only delays him a bit.
I think only the spur of the moment killer can possibly be inconvenienced by any law. This may be worth doing , but eliminating easy targets would do more and would work against the careful planner also.