Well, I think I know what it IS, I just didn't know you could DO that!
It sure looks like a Swedish Carl Gustav small ring Mauser action. Without a date, I don't know if it is from a 94 carbine, 96 rifle, or 38 short rifle.
All Expert Sources are opposed to converting a small ring action to .30-06. I guess the Swedes had more faith in their steel, eh? (I had a CG 63 .308 target rifle on a 96 action and it did ok.)