I have partially 'neck sized' new brass in loading it for the first time, with good results.

I did check to make sure the partially sized cases would fit into the Krag's chamber and allow the bolt to close.

I also trim case length with a Lee .30-40 case trimmer, before loading. This makes for nice uniformity and precise Case Mouths.

I often neck-size my Krag Brass using a Lee Collet Die for 7.5mm Swiss. This only Sizes part of the Neck and is very easy on the Brass. (No pull of an 'expander-ball' through the sized neck).