What is the"radius stud package", as in the 586-1?

I have asked the very same question myself. You really need to have one apart to "see" the differences. On the older guns, the hammer and trigger studs were set flush with the frame and the holes through these components were simply drilled straight through. If you ever have a newer gun apart, you will see the holes on the hammer and trigger are slightly counter-sunk and the studs have a raised area where they are installed in the frame. That allows more bearing surface for the parts to ride on and reduces the possibility of stud breakage (shearing), which was more common in the heavy magnum calibers.

Now....this explanation is in my own words and not "machinist talk". It resulted in a stronger package and reduced stud shearing. I hope this makes sense. It's how I resolved it in my own mind.

Thanks Snubbiefan. Your explanation was great. Now that I have read your post I know exactly what you are talking about, and I have seen the two different methods of construction.