fsa46,
My 300 has one (1) spring.
For the future, I bought a replacement Maccari spring (31 coils x .105 wire) :
http://www.airrifleheadquarters.com/...88/6759574.htm
FYI my 300 makes about 658 fps with JSB Match Green (7.32 gr.), for a hair over 7 ft.lb.
By comparison, my 300SU makes 640 fps with RWS R10 Pistol (6.99 gr.) for 6.3 ft.lb.
This is quite a nice video discussing the single spring use in the 300S series :
https://www.youtube.com/watch?v=LRV42p9GjXk
Have fun & a good weekend
Best regards
Russ