I read the thread regarding the "unknown" grenade launcher that someone attributed to the M1941 Johnson rifle. While it can be hard to prove a negative, I do not believe the launcher was made for the Johnson rifle. I base this opinion on several factors: (1) There is nothing in any Johnson factory documents, reports or anything else pertaining to the development, or even the concept, of a grenade launcher of this type for the Johnson rifle. (2) All M1941 Johnson rifles were manufactured under Dutch contract and the Dutch did not request grenade launchers. (3) The Johnson rifle was never a standardized U.S. military weapon, thus little, if any, perceived need to come up with a grenade launcher. (4) Only a relative handful of Johnson rifles were ever procured by the U.S. military, thus no pressing need for a grenade launcher. (5) Actual combat use of the Johnson rifle by the US was virtually nil. Again, no use - no need for grenade launcher. (6) I'm not sure that the recoil-operated Johnson rifle would be conducive to the use of a grenade launcher. I suspect that the heavy recoil generated when launching a rifle grenade would wreak havoc on the rifle's mechanism. I would speculate this may be one of the real reasons why a grenade launcher was never seriously considered for the Johnson rifle. (7) Following up on #6, "The Book" discusses Melvin Johnson's idea of a "auxillary grenade launcher" which was essentially a special barrel assembly that replaced the standard barrel assembly of the Johnson rifle (and LMG). This would only be necessary if the standard barrel assembly was not suitable for use with a "conventional" grenade launcher. I would have to see some evidence stronger than the existence of an unmarked launcher with no provenance that may happen to "fit" on the barrel of a Johnson rifle (and probably other weapons as well) to suggest that the item was, in fact, a factory made item for the Johnson rifle. I do know that some reproduction carbine grenade launchers are unmarked and modifying one to fit on a Johnson barrel probably isn't too difficult.