This is a long story that started out well as our own subsailor74 donated a lightly used 257 AI chambered barrel for my Sako that required a new barrel. Penny wise and pound foolish I gave it to a friend who has the skills and equipment to fit it up. He lacked the one piece of knowledge that would have made this work out, the metric threads are not what he thought they were. Oops, so now I have lost the tenon of the previously chambered barrel and that amount of barrel length, not really much of an issue, however a complete chambering and fitting is now called for.

So whom has either the 40 degree 257 AI reamer, or the 25 Souper to get this show back on the road?

Stick with the 257 Roberts...you don't really gain much over the AI version, maybe 3-5 gr powder and 100 fs if you believe the BS, and the standard is slightly bigger than the 25 Souper by the same amount or 25 AI Souper, other than bragging rights of a sort.

If you want more pizzazz go with the 25 WSM or RSM versions and gain about 20 gr more powder...25-05 range in a smaller package.

4D reamers has all those reamers and more in 25 cal.

I've done several AI versions over the past 40 odd years and the only one I have left is the 250 Sav AI which you DO gain a large amount of velo over the standard...I equal 257 Roberts with several loads except when using the 117-120 gr bullets. I also wanted to do a 25 souper but just never found that round toit to doit.

Argumentatively, all the happy horse shite about the AI belongs in the distant past...the cartridges we have nowadays have superseded the gains the AI had, but the AI mysticism still hangs on...NO diss or flame intended...nothing wrong with nostalgia.

You've been around long enough...pick your poison and get on with it...and don't second guess.

I like some of the A/I cartridges and feel they still have some worth even today.

I'd just rechamber in standard 257 bob and use the plus-P cases and loads.
if you really want more than that, step up to the 25-06.
for deer to 200-250 yds, you gain nothing but getting the bullet there a millionth of a second faster.

I wold go the 25 Souper. MUCH better/stronger brass the the 257 Roberts unless you make it out of NM 30-06.
Just my .o2

Just my opinion, with the 25 souper you can use Lapua brass. That would be selling point for me.