Ain't the body of the 44-40 about .010 smaller in diameter than the 45 Colt? The little longer can be trimmed. I suspect the base area would not expand. Do you still full length resize? Or just the top "neck" section?
Once fired in a 45 Colt chamber, you would full size in a 45 colt sizer die. The case is now a 45 Colt, with a thin mouth, but with a 44WCF rim.
Check the length, and trim if necessary.