Towards the end of WWII Frankfort Arsenal was still working on a blank cartridge for use with the Blank Firing Attachment (BFA) that was in development. The war ended and neither the blank nor the attachment were ever standardized or produced in quantity.
This blank is one of the reasons why knowing nomenclature is so important. One look and you will see it looks very much like the M6 Grenade Cartridge for the carbine. However the M6 is a full powder charge and will destroy a carbine and injure the shooter if fired with a BFA.
To make matters worse, a Texas company during the 1970's made reproductions of the BFA.