forward allowance, shotgun lead

Shotgun lead is normally just done instinctively, like catching a ball you don't really calculate where to put your hand to catch it you just do. Its the same with shotgun lead but there are 3 main ways people instinctively generate lead. Here are 2 videos to show you the 3 ways.  

This table is just to give you an idea of what amount of lead is needed. This is with standard eley velocity cartridges