Using the UK newspapers stats of 1.3 million shotguns and 525,000 ish other firearms owned for 2015 and taking the 2015 population at ~65 million gices us a rough firearms ownership rate of 0.02807 or about 2.8%. The US has 357 million guns according to the Congressional Research Service (in 2013), and a 2015 population of ~323 million.
Now I can't spend time digging to dind the exact numbers because I am at work, but a quick google puts the 2013 UK gun homicides at between 40-44 depending on what I saw. so say 40.
40 gun homicides for 1,825,000 guns, or about 0.000022.
US had 11,200 for 357 million guns, or 0.000031
Now, the UK only counts as homicide an incident where the case lead to a conviction. This biases their numbers low, and in that case it is worth it to note that only about 62 ish % of gun homicides in the US lead to convictions. I dont have those numbers off hand so I am rounding. That means that the US rate, if counted like Britain counts it, would drop by almost 40% to about 0.000019, or less than Britain on a per gun basis using Britain's method of reporting homicide.
All in all, I think we are doing ok. I am aware stats are counted on a per capita basis most often. However, seeing as our 2014 homicide rate was the lowest its been since 1963 I don't feel threatened.
If you are interested, in 2014 there were 8,124 gun homicides. Our gun homicide rate was about 2.5 per 100,000. I am fine with that.