[Zachary]

280 Ackley Improved vs 7mm SAUM

If portability is a concern, then you will want to get a shorter action rifle - hence, the SAUM. I am not sure how long any of the SAUMs will live, but it shouldn't be much of a concern as I think that you will probably be handloading.

Zachary

 

[Rocky]

Consider Availability And Such

If you haven't already, you might want to take ammo availability into consideration. May not be a major concern, but not everybody has 7mm SAUM or even .280 Remington in stock. (You could use factory .280 Remington in a .280 AI in a pinch.)
Since portability is a big factor, maybe consider the 7mm-08, or similar, in a short-action lightweight rifle as ammo is readily available.
For a custom gunsmith, check with the American Custom Gunmakers Guild - www.acgg.org - members of the guild are required to meet certain standards (ethics, skill levels, etc.).
Whatever gunsmith you choose, it would probably pay off to see some of his work and talk to a few customers he's built rifles for before commiting yourself. Be sure to ask the customers if the rifle was finished on time and as promised.

Rocky