I've made several machined cases for 30/40, 308 and 45/70. Mine were all made as reduced capacity cases for better load density. My most successful one was made of 304 stainless steel with a internal capacity of 1.9cc's. It had a .250 hole back to the primer area but the neck was reamed .3115 id and chamber size .340 od. It lasted for years but, gas finally got behind it and collapse the neck. There was no saving it
but, I doubt if it ever could have had a head separation though. I also made a 30/40 out of bronze with a .3125 drilled straight chamber back to the primer pocket. It was 2.8cc's. note here, you need to leave a thicker head area for machined cases. Most drawn cases have a head thickness of about .200, I made mine leaving the head .250 behind the drill point. The head area is going to be softer and weaker than a drawn case, no matter what you do unless you use stronger materials like SS or aluminum bronze. The 45/70 I made with a .375 hole back to the primer. All but the 45/70's were made for small primers.
I would say that the biggest advantage of the machined case is that you can fix any head space issue you might have. I didn't find the "magic bullet" I was looking for in case capacity or primers ( I did have some success with the stainless case). But, I can stay one thing, That little stainless case saved a lot of powder!
One other thing, for those that would make them. The inside of the neck has to be very smooth. Do not just leave a drilled finish if you ever shoot it fixed. The bullet will grab the roughness and take the neck with it!
Joe, did you anneal your cases before reforming them?
Frank