I can't because I didn't do the job myself. It was beyond my knowledge and understanding. The guy who did it, a Slovene gunsmith and airgun aficionado, told me installed a custom made spring, a modified piston and also modified the cocking mechanism. He told me not to try to disassemble the gun myself since I will not be able to reassemble it without help and special tools due to the piston design and the spring tension (If I have to get it serviced, I go to his workshop). He told me he based the mods on the GAMO Magnum GR 25, if this can help you. To be honest, I removed the stock but the only thing that really stands out is the beefed up cocking lever (The stock was also modified to accommodate it).Can you explain the mod(s) that elevated this springer to a 50fpe capability?