It is better to pay a premium if you get to inspect the rifle, and it is in excellent condition.
When you order, you get pot luck. I got so discouraged by the crap I received from importers, I canceled my collector's FFL.
If the rifle has a Walnut stock, it is worth a bit more. The beech stocks do not have as much figuring, or have the colors that Americans prefer. They are totally functional and fine stocks in all other regards.
The Swiss K31 will shoot GI 174 FMJ's very well. I have not tried 150 gr FMJ's, but I don't see any reason why that rifle won't shoot those very well.
You will just have to adjust the front sight for windage, and the rear for elevation, when sighting in.