I've heard that most smiths will not tap a H R 12. My son has a 20ga and we epoxied sights on the barrel, they are not coming off!! I have heard of many folks epoxying on a scope base. Also you might be interested to know that over on the shotgun world forums is a fellow named Mike Orlen who will thread a barrel for chokes for 35$. He has highly recommended on the forum and has a lot of feedback. I have not had him do any work, but am planning on it. My sons is mod choke also and we got good patterns out to 35 with hevi 7s. I also filled the hole in the buttstock with lead shot to reduce the recoil of the 3 inch mag shells.