Back in the 1960s I had one of the Mattel plastic TOY M-16s. It had something like a speaker inside the magazine. It was pretty loud. Of course it broke pretty soon,, right were the fore-end met the receiver area. Probably from Butt-Stroking my cousin in the head.
The GET SMART Agent 86 radio / folding submachine gun was a much better product. As was the James Bond 007 plastic attache case with the concealed dagger and plastic Luger carbine that shot hard plastic bullets.