Quite a simple job, actually, for a .22 RF or low pressure Hornet.

Action strength is the big one here, imho. Seems to me, most or at least many Rook Rifle's of the period lack the necessary strength. You did not note the action's make, date of mfgr, etc.
A small Martini would be fine, but a light single drop barrel I don't know?

BP loads, of course, would likely work just fine.

The .22 Hornet is very close to the .22 WCF that preceded it. The WCF was first a BP round, later loaded with low pressure smokeless loads.

Ned Roberts shot a few deer with a .22 WCF, 45gr. Lead bullet at about 1,400fps, back in the early 1900's.

The 5.5x50R (5.6x50R)seems too high a pressure ctg. for an old rifle.
It is listed as a 49,000PSI ctg., 44,000CUP.
http://kwk.us/pressures.html