My favorite Mattel toy gun (never got to own one, just saw it on TV) was the “MMP” which I guess meant Mauser machine pistol. It was a Broomhandle Mauser looking thing with a windup machine gun sound.
I think my first cap gun was given to me back in 1957, and being that westerns were all over the television at the time, I tended toward plated die-cast "cowboy" rigs until that Mattel Tommy Gun came along. Around the time the Mattel broke, I was given a black plastic "Schmeisser"-looking toy gun that clacked and simultaneously had a red plastic piece move in/out of the barrel end... not as loud as a cap gun, but loud enough to get me ordered outside PDQ.
Mr. niteowl77