not authorized but documented
https://www.milsurps.com/showthread.php?t=56965
The army even put out a Technical Bulletin showing how to use a 60 mm M49 mortar shell as a rifle grenade. It did not authorize its use, stating only the ground commander could in an emergency. I made up a dummy for display (can't have mortar shells in N.J.) using a restored M1icon projection adapter. It was not to be used on the M1 carbine!!..
Page 20 - 21 Company Commander by Captain Charles Brown MacDonald - Charles B. MacDonald (November 23, 1922 – December 4, 1990) was a former Deputy Chief Historian for the United StatesArmy. He wrote several of the Army's official histories of World War II.
"The main request was for several types of ammunition, including 60 mm mortar shells adapted for firing from the M1 rifle with the aid of a grenade launcher. My men had found the the expedient to be most effective in street fighting in Brest and swore it was that it was more effective than either hand grenades or fragmentation rifle grenades. It, in effect put the equivalent of 60 mm mortars in the forward foxholes"