Q. How far does lead shot travel? Does shot weight make a difference?
A. It depends on several factors, there isn't a definitive answer to your question, Brendan. What we must be aware of and abide by though, is the recommended distance in front of the gun which is known to be a safe zone for shot to travel through and fall on - 300 metres.
Many years ago, I heard a story that told of a cartridge maker who tested his cartridges on a canal, firing into the air at different angles towards another who marked the ripples from the shot entering the water by which they could establish distance for any given load. Whether it's right or not I don't know but the figure of 215 yards quoted to me from this heresay appears to be within the realms of possibility, given data available from more modern testing. Several research papers are used to quote the distance that lead shot travels although they mostly point to the same set of results so what follows is as a guide only, it isn't to be taken as an excuse to shoot with less than a 300 metres safety area in front.
So how far does shot travel, then?
Firstly, we have to consider the angle of elevation at which the gun is fired; there is an optimum angle at which lead shot will travel the furthest when shot from a gun. Most people will tell you that the gun needs to be held at 45º from level ground when fired but this isn't the case - it would be if we lived and shot in a vacuum, physics shows us the shot would proscribe a parabolic arc which would make things far too easy for us. As we are surrounded by air, the shot has to overcome air resistance and friction so the angle a shotgun needs to be for the shot to travel furthest is 32º-33º from level ground. Pointed higher or lower than that will make the shot land sooner, i.e. shorter than it's maximum distance.
Secondly, we have to consider the wind velocity. If you shoot straight up into the air it is unlikely that you will be hit by the falling shot from your gun, a hefty breeze will blow shot up to 70m sideways so it follows that a wind from behind you when you pull the trigger will help the lead travel further and conversely, a wind in your face will shorten the distance it travels.
Thirdly, we must take into account the size and weight of the lead pellets in your cartridge. The larger and heavier the shot, the further it will travel. US shot size 1 (4.06mm) could travel about 350m given the right conditions whereas US shot size 12 might only travel 110m.
So, given all this, how far away can we as clay shooters expect to see our shot land? Most of the results from tests suggest that common clay shot sizes will travel between 160 and 215m which all makes sense of the safety zone if we take a strong wind into account. 9 shot will cover the shortest distance while 7 shot will travel the furthest.