Joe_S,

  Probably not a great deal, if any benefit will come from neck sizing a .45/70 case. But if you wish to try it the quick and dirty way is to turn your FL die out a full turn. If it does show an increase in accuracy then there are neck sizing dies available.

  I am assuming you are using BP. If so then some current thinking is that you should use no neck tension, or just enuf that the bullet is a thumb press fit.

  The other method, which I use, is to use an expander plug that will open the mouth of the case to .001" under bullet diam. You will need access to a lathe, or someone who will make a plug up of the appropriate size as the standard expander plugs leave the case mouth anywhere from .003" to .004" under bullet diam. This is fine for jacketed bullets, but not cast Lead...... which I also assume you are using.

PETE