Hk import montefeltro recoil spring swap ?

[winchester1852]

well i have this monte that needs a new recoil spring, i cant figure out how to get the recoil spring plug out, there are no flat areas for me to get a cresent wrench on its just thread. the original plan was for me to

use a jam nut as a flat area to grab onto with a cresent wrench but i cant find the specific jam nut needed. any help or suggestions would be much apprecated


Cheers