Hey Hawg,
I found they were manufactured for the .44 Henry and both .38 RF & CF (smaller rigs).
Info is sketchy, but some dimensions of the cylinder & frame are listed in
"A Study of Colt Conversions and Other Percussion Revolvers".
On the .44 calibers, I have read the frame was the same as the 1860, but without the water table.
They would had to move the position of the chamber out at least 0.030" from center to get the rim fire cases to fit.
This would require a different barrel as the distance from arbor to bore has been changed, which they did use a different barrel.
One would think it would have been easier to go with the .44 Colt, making a Long Cylinder type instead.
They did extend the front of the cylinder so the flash from firing didn't spray directly on the arbor.
Somebody might chime in who has access to an original, we might discover they're thoughts yet.
AntiqueSledMan.