Tuning Putting a spring into the gamo magnum igt mach 1

I want to remove the gas ram and put a spring inside this air rofle(personal preference)

Does it require a new piston, seals etc or do I remove the gas ram and put the spring in the original housing unit. 

Generally speaking can you put springs inside airguns that were manufactured as gas ram, such as Benjamin Trail Np Xl, mag tech n2 extreme, hatsan 125 sniper,.?