This is a patent drawing filed on Nov. 21, 1941 for a grenade launcher that can be used on the M1icon or M1903. What is interesting is that there is no provision to to disable the semi automatic function of the M1. This could indicate that the Army was testing grenade firing M1's without disabling the gas system. This also could explain why the SA and Winchester started annealing receiver heels; in anticipation of increased battering of the heel caused by a functioning gas system.

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