Since the widespread use of rotary machines, it is not as easy as it once was to get two birds fairly in range over the decoys.
When using a rotary device the first pigeon to come in will invariably turn off before the second one is in range.
In the ‘good old days’, you simply let the first bird of a pair land amongst the decoys (which it would happily do) then kill the second bird as it came within range, taking the landed bird as it flew off.
In this way, it was not unusual for me to kill 50% of my bag with doubles, i.e. 25 right and lefts in a bag of 100.
Now, it’s not unusual to shoot 100 pigeons, and not make ONE double in the day!