I'm in the same boat. I called Mossberg Customer Service, they want to know the serial number of the my 930 JM. After I gave it to the CS rep, he tells me he can't sell me a spare carrier (Mossberg's term for the lifter) because the JM series is new, they aren't selling parts for it yet. I would rather send a spare lifter to C Rums and have the original handy just in case.
Anyone tried a regular 930 lifter in their JM series?
Most likely its the same thing