I don't know if the 1885 action is big enough, other than that, I don't see why it wouldn't work. I have read a lot about such conversions on the Ruger #1 action, and it can't be that much bigger than the 1885 High Wall action. Bowen Custom Guns (the guys famous for BIG revolvers) used to do a lot of work like that on the Rugers, and so does SSK Industries. You might contact them and see what kind of advice they would have for you. I wouldn't try to do a project like this on a H&R action, if you are going to spend the $$$ to get a classic Nitro rifle, do it with a classic rifle.