All brands of receivers will use a different thread pitch, that keeps them different so you don't just get the wrong barrel and put on your rfile. Some will have a slightly larger diameter as well.
I don't think you can order one for the Sako from Midway, but I may be worng on that. I would suggest that you contact someone like Douglass Barrels or Pac Nor and send it to them and let them fit it for you. MOst barrel makers offer the service and should have the info you will need to get the right barrel ordered for you.
I am not sure about the contour of your barrel, how big is it at the muzzle and at the receiver? I would see if you can get a fluted barrel for it, that can save you around 6-8 oz's. Cutting off the barrel would normally be what I would do on the barrel, but you have the 7mm Mag and need all that you have on it unless you reload and use a faster powder.