I think I have basically perfected the above process. It is as follows:
1) Procure 30-40 Brass
2) neck down to 7mm with 7x57 size die with internals removed
3) Neck down to .25 with the 25 Krag AI 40% die (mine are RCBS, may need to get them from CH4D) with the internals removed.
4) expand to .25 with the Lyman 25R M die.
5) Anneal necks
6) Load with reasonable load (the 25 Krag AI has 2gr. capacity greater than the 257 Roberts AI and 2gr capacity less than the 25-06. I have data for both.)
7) Fire in 25 Krag AI chamber. You are done. Neck size and have fun.
Bulberry Barrels has the reamer and made my Encore barrel.