This poster is an 80s classic, the stats are from 1985. The situation is much worse today - in 2011 the figure for gun related fatalities in the US was 32,163, compared to 146 in the UK.
There are A LOT of people in the USA, so it is more meaningful to compare the number of deaths per capita - an individual in the USA is only four times more likely to die in a gun-related incident than in the UK.
There is approximately one privately owned fire-arm per person living in the USA, while in the UK there is one gun for every 16 people. This means that every gun in the UK is four times more likely to kill someone than a gun located in the US. In the USA guns are responsible for four times as many deaths, but in the UK you are four times more likely to be killed by a gun.