The murder rate is not the same thing as the asshole gun nut goes ape and massacres a bunch of people rate.
That particular rate has gone up in recent years, because there are more gun nut assholes with more dangerous guns.
That kind of guy is rarer than one in a million.
Right now we possess more than one gun each, tho the distribution is not even.
How much gun confiscation would be required to make one gun hard to find for that one in a million guy?
Then of course you would really need to gather up everything elese that these guys could use, Knives cars , airplanes and hammers.
If you don't gather all of the dangerous stuff , you will have never done enough.
In the meantime , the normal( rational )criminal will have run of the place, and that type is a lot more common.