Matt,
Why? Ku-dude

Area gunshop has one I could get for ~$100. Seems like a nifty enough rifle for that money to go out to the local range and bang at targets at 50 yards. I don't need to stock ammo for yet another caliber. I know the 7.5 is 55 mm ....does that mean turning the barrel back a bunch (meaning expensive) to go to the shorter .308?

In the big picture of things it's a bit of a "what if" question. If it's something that will cost $250 bucks to do,then I realize it's kinda dumb to do. Spend $250 to save twenty bucks on ammo cost isn't the dumbest thing I've done...there was that machine I bought that converts diamonds into jelly beans.

There is really no way to ream the 7.5 swiss to 308 case the 7.5 swiss case is the same size as the 284win. I guess one maybe could set the barrel back a bunch, but If I remember corectly the k31 has a weird barrel shank and thus setting the barrel back would be a no go. There are a few out there that have have had a 308 barrel put on but these are mostly 1911 models. a 308 barrel can be put on but it requires special fitting and machineing, beyond what most gunsmiths can do. I have seen where one could have their gun rebarreled with a 308 barrel but its expensive like $500+. If you reload just form brass from 284win and use regular .308 bullets and you are good to go