Does anybody know a good tutorial on replacing a mainspring for a gamo big cat.

GAMO AIR RIFLE SPRING AND SEAL DEAL KIT BSA MK 6 MK 7 VIPER WHISPER BIG CAT CF30 SHADOW .177 .22 https://www.amazon.com/dp/B0736Y1J4Z/ref=cm_sw_r_cp_tai_eP1kCbTYBRYPD

You may want to check this out. Replaced spring and seal on a gamo 220 hunter with their kit. It is like a new weapon. Also replaced spring in varmint with their piston and seal. Their stuff works. 

Charlie