I picked up two a Gamo Whisper Slent Cat and a Hunter Extreme both in .177, the Hunter Extreme would cock but not lock.
You must have a srping compressor to reassyemble these rifles, not necessaraly to disassyemble scary shit happens when you pull the pin or bolt on a compressed spring.
My grandson just turned 12 and I am getting him ready to start hunting with us so the Whisper Cat shots at 1250 fps is light wieght and has fixed sights (took the scope off for now) figure we would get him started on Rabbit and such.
the Hunter Extreme shoots at 1650fps, (installed the trigger and spring catch properly) wieghs 9 lbs! wood stock Bull Barrel and no sights just the scope. Trading it down for a lighter rifle with sights.
But I am a DIY guy, why pay someone when you can but the tools and own them and grow your knowledge!