The 2400KT is not equipped with a hammer spring adjuster and we do not sell one for this gun.
Generally speaking, a "hammer spring adjuster", like the one that comes on the 2300S, allows for slight adjustment of velocity. Its main function is to fine tune the usage of CO2 for a longer "flat curve".
We do not recommend customers modify or disassemble their guns, other than what is described in the manual. An exception would be the steel breech kit which comes with instructions.