This looks like a reputable page for the Garand M7 launcher.
M7 Grenade Launcher


I was having fun looking around in the link that Von Poop posted, and found this. This is new to me. A Pz.B.39 converted into a weapon for firing the rifle grenade.
Lone Sentry: German AT Grenade Rifle (WWII Tactical and Technical Trends, No. 37, November 4, 1943)

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