The Thompson-Hoffer conversion requires a special "cartridge holder" which is a steel case to fit the chamber and work from the magazine (these are around $100 nowdays). The Thompson-Hoffer was chambered
for the 22 short cartridge only. Some have rechambered them to fire the 22 Long Rifle but the twist is not correct and not very accurate.

You would be better with a 1903 made in 22 Long rifle (M2) and they are very accurate and do not overlook the Lee Enfield 22 Long Rifle conversions either