Let's see if I'm understanding this translation right.
You want an ABS that will, when you press the Z button, it'll show a gun. A specific gun? The gun equipped to the player? What do you mean by show, will the character sprite change to show he/she is holding a gun, or do you mean a picture of a gun?
I could not understand the rest, honestly.
You want to have your weapon, gun limited to 7 rounds of ammunition? And when you shoot a monster 5 times it runs away? I'm very confused, what is your native language? It might be easier since your translator is butchering whatever you are intending to say very badly.