Good, glad the problem is solved.
On hard receivers, I always used a torch and a fine flame, but got taken to task by someone (I think on here) for being old-fashioned and was told that an electric soldering iron would do the job, so I mentioned that. I guess he was wrong. But it's a good lesson not to take someone's word for something.
Anyway, none of those Mausers are as hard as M1903A3 Springfields, which are really hard, maybe even harder than the old SHT receivers. I don't think anything but a torch will anneal those because they are hard deep down, not just on the surface. Of course, I wouldn't touch an SHT receiver; I once turned down a sporterizing job on one because I never trusted those receivers after breaking one with a hammer.