The adjustment from RF to CF takes place in the horns of the lever. The 4A Cadet lever is straight hand, the 12/15 is pistol grip. It is not as simple as swapping trigger groups or just levers.

That SAIS I referred to in an earlier post tells the correct procedure for adjusting striker impact. That is the procedure used by BSA to make CF rifles from RF.

You will have reduce the striker and Bush the breech block when converting to CF. Some Smiths will square your breech face, but the change is virtually imperceptible and unnecessary.

To make 17HMR I put 17 barrel liner in 1215's. My 17HMR 1215 is my go to favorite gopher gun.