also the laquer coating on the 5.7 X 28 cases did not burn off at 500 degrees... my buddy is going to try 900 degrees this afternoon & see if they'll get soft enough...
I don't have much experience in metallurgy, but it is my understanding that exceeding 800 degrees F for more than about 30 seconds is going to cause irreparable damage to the brass. (Causes the zinc or copper to oxidize - can't remember which.)
On a separate note...
I have been a fan of the centerfire .22 Mag concept for a long time. For a while there, I was even trying to get my hands on some .22 CCM cases. As you probably know, that is incredibly difficult.
Which makes me wonder: Why do you want to use 5.7x28mm cases, and not .22 Hornet?
The only advantage I can think of, is that you won't have to ream the case necks as much, since the cases don't have to be trimmed as far (if at all). But... the 5.7 case doesn't save you any time during the important forming steps (swaging and lathe-turning).
Am I overlooking something, or is simply it a matter of convenience? (Such as having several hundred pieces of 5.7x28mm brass.)
I like "FN Dog".