Hi Neil,
Just check the rules I have put up again on the BBS again today and hopefully all will be explained.
6 yard MPL Postal Competition Rules - read the pistol rules - scroll down to the next thread regarding .22 air pistols and then - scroll down to see the rules regarding air rifle (based on the existing 6 yard MPL rules for air pistols).
Its dead easy really - each card has five air rifle targets on it.
Shoot one shot at each target to give 5 shots on each card.
Shoot 6 cards per month and score them yourself and email the scores each month to this address. 6ydmpl@gmail.com
If this retard can do it - I think you will also be OK