I doubt a 5 shot J frame .40 S&W is possible. The j-frame cylinder
already is limited to only 5 .38 Spcl/.357 Mag. You'd need
the K frame at least and S&W would probably lean
toward the L-frame although the 610 10mm/.40 S&W is an N frame.
& a .45 ACP in an L frame also doesn't work - by the time
you get enough outer wall thickness the extractor in the middle is
too pinched/no room to operate