ok, ive got my sport 48 12g infront of me, s/n 307xxxx.
take off the big nut that holds the fore stock on
remove stock, then barrel
pull recoil spring off of the mag tube
pull the grab handel straight out of the bolt
pull the bolt out of the front of the reciever
I have never removed the firing pin, so good luck
to reassembel, you hafta get the 2 fingers on the back on the bolt to go around the hammer and into the pring for them. This is a PITA if you dont remove the trigger group
knock the 2 pins out of the reciever above the trigger
remove the trigger group
the shell catch will be lose and can come out
drop the bolt back in the reciever and align the fingers up in the bolt spring
put in the bolt pull handel
put in the shell catch
put in the trigger group PITA to get it and the shell catch lined up right
drop it in under the bolt then slide it backwords
put in the pins
put in the recoil spring
put on the barrel
put on the fore stock
put on the stock nut