YOU SAID:

i shoot a boy with my gun

INTO JAPANESE

私は銃で少年を撃ちます

BACK INTO ENGLISH

I will shoot the boy with a gun

INTO JAPANESE

私はその銃を銃で撃ちます

BACK INTO ENGLISH

I will shoot that gun with a gun

INTO JAPANESE

その銃を銃で撃ちます

BACK INTO ENGLISH

I will shoot that gun with a gun