Just gonna put it out there but... upgrading a crossman gun... not being age verified... etc. etc. it's kind of hard to take your inquiry seriously.
But that aside, to answer your questions not all models of a gun share internals. Different manufacturers use different internals, so even if they are the same gun model, they may not be entirely compatible. Do some research on the net to learn about compatibility. Also crossman airsoft guns are really just clearsoft, and are entirely not worth upgrading IMO.
In regards to decreasing the ROF on any AEG, you have two options. Either get a lower torque motor, or increase the torque required to cycle by installing an upgraded spring set (it is also recommended to get a corresponding gear set/internals to hand the stress in this gase), or get a torque up gear set and keep the original spring. A combination of the above will work as well.
For GBBs you can either have a heavier blowback body or increase the weight of the blow back components. It is very difficult to fine tune FPS with GBB mechanisms as far as I know.
For further help I recommend you get age verified, and purchase a brand name quality AEG, as this will open up many more upgrade options for you and allow you to create the set up you are looking for. Good luck
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