I don't smoke crack there??
and when shooting full charged load that cause the case to expand, there is a chance of case separation as it forms the new chamber??
this isn't made up info
as for anneal brass YES
but again,
I am stating that fire forming NEW factory loaded ammo to a MOD chamber, , your NOT having the chance to anneal it, as its live loaded ammo!

as for why I used a separate chamber, it was to just get brass formed, and NOT spec MY rifle I planned to use it in, BUT darn close
and after that once loaded in my shooting rifle, it was then formed to MY chamber on THAT rifle

I simply used the extra chamber to fire form brass and NOT fill my barrel with corn meal!
there was a reason to my madness(as I guess you see it as??)

I learned this from Bobby Hart, of Hart Rifles A man that kinda knows a LOT about guns?? and wild cat calibers
been a good friend of his, his dad and his Grandfather(many moons ago when he was still with us)
and DON"T think it was bad advice or practice!
worked for me??