I GOT IT!
In the end, calling the BP Father of arms I have achieved it, now it needs to be logically polished … like anything that is implemented.
But working it works! When I pick up the AK my FireDelay is 1 (as the database says) and when I pick up the gun it is 2, the FireDelay thing was just a test, now that I know how it is implemented and how it works I will modify all the variables, damage, precision , reload, ammo …
Thank you very much again, I had been trying this 4 afternoons without result.