A slight correction on the numbers, Brian...
218 Bee - ~0.075 cu in, ~18.9 gr H20.
Hornet - ~ 0.057 cu in, ~ 14.3 gr H2O.
Jet - ~ 0.074 cu in, ~ 18.8 gr H2O.
221 FB - ~ 0.088 cu in, ~ 22.1 gr H2O.
The "improved" versions are slightly higher in capacity.
(Slightly OT) The Hornet has a large following, especially in the 14, 17, 19, and 20 cal versions. It is very efficient, uses very little powder to get fairly high velocities. Anyone interested goto Sabier...lots of very satisfied customers there.
Accuracy of the Jet depends on all the usual factors...tuned rifle, tuned brass, tuned load. The Jet would/should be much more accurate and attain a higher velocity in the Handi's longer barrel, but would still suffer from the same problem of the case moving backwards against the frame and locking it up. How much of a problem depends...and the only way to know that for sure is to shoot it.
Luck