I am converting my mod 85 low wall from 32 rimfire to 32wcf. Larry Potterfield of Midway has a video showing how this is done and I once converted a 22wcf to 22 lr. I had no trouble drilling the 22wcf breach block with a hss bit, and Potterfield does not specify a carbide bit for the 32 rimfire block. My 32 rimfire was made in 1901. I tried using a new hss bit to drill out the rimfire pin hole to plug it and it was very hard to do. A new drill bit would not even start a hole for the new center fire pin. It appears that the breach block is made of very hard steel or has a thick surface hardening. I have a couple of carbide bits ordered which I hope solve the problem.
Does anyone know if Winchester made the breach blocks harder after a while? Did they use harder steel to make the rifle stronger for smokeless powder loads?