Vic,
You are correct,bending the rim forward is exactly how it works.
Otto,
The 45-70 case is placed in the die, the punch is inserted into the case and force is applied to the punch(in my case,by a press)to force the case into the die. If you make one,make a recess of a diameter to closely the 45-70 rim.This is just to "locate" the case,so depth is not critical. Inside this recess,and concentric with it make another,slightly larger than the solid head part of the case head(about 1/2" depending in the particular cases to be used).This recess should be deep enough to "make up" the difference in rim thickness.If the 45-70 rim is .070" and you need .095",the depth should be .025",plus a couple thousanths for "spring back".I made the punch to fit inside the case pretty closely and hardened it.I was learning to make cases from 7mm mag and 8x50R Lebel, so I needed to apply a lot of pressure. Using 45-70 cases is so much easier that I'm not at all sure the punch needs to be hardened.Handloading will be a lot easier to you,because you are a machinist."A lathe is a necessity of life".
Mike
