Thanks guys for your response s . I tried shortening a rivet by removing the center pin (not sure if that is what it's called) and cutting off some of the rivet body  to make it shorter . But when tried to set it , it would not expand .  I am using a piece of wood to practice on . I looked on youtube about using a nail for a rivet but not sure I am brave enough to try an hammer on the hand guard , afraid I would wined up damaging it .