What you found is a very common occurance in new manufacture rifles. I believe the factories cut the throats long in order to keep handloaders from doing exactly what you're trying to do so they can reduce their liability if you blow yourself up.

The only thing you can do is seat your bullets as long as you can and still have them function through the magazine (3.610" in a 7mm stw M70). Try changing the seating depth backwards from that but my experience has been that you generally won't get better accuracy that way, but try it. My serious hunting rifles all wear custom barrels. When building them I send dummy rounds to the gunsmith and told him to cut the throat so the bullet touches the lands. Now I can seat bullets to touch the lands and still have them cycle through the magazine.

You mentioned that you just got your STW back, I'm wondering if you had it rebarreled? If you did then send it back to the gunsmith and tell him he cut the throat too long. Have him set the barrel back and recut the chamber.