I am curious. I know that gunsmiths flute the bolt to reduce weight, but is there a functional reason for spiral verses straight fluting? It seems to me that spiral fluting provides a more direct channel for crud to get into the magazine well, where properly positioned straight flutes would not. Straight fluting would also be much easier to machine, so is spiral just for the cool factor?

Yep, cool factor.

I've never played with a fluted bolt, but my impression is that a bolt with straight flutes would tend to hang up or pull sideways the top round in the mag. As the bolt is turned, the shell is going to rise into the flute and then get pushed back down. That can't be good for smooth operation. With a spiral flute, the shell would be pushed down at all times, but I imagine it might rock a bit. The spiral flutes I've seen tend to be wider than the straight ones, which I think reinforces my position. I could be all wet, but from where I'm sitting I would think the spiral would be preferable (functionally) if you are going to flute to save a fraction of an ounce or join the cool kids. I can't imagine any reason to flute to improve function or accuracy. Maybe if you dump a pile of sand on the action a fluted one would bind less but I've never seen any evidence of that.

as way once said but changed to fit the subject
Only anew orleans pimp would think spiral fluting was anything but ugly and worth less

As gzig5 stated, straight fluting can cause cartridge "ratcheting" as you open the bolt. This is why most people prefer spiral fluting. I will only cut straight flutes on single shot bolt actions for this reason.

gzig5& h2oboy are correct unless the straight flutes are properly sized they can cause issues. Got a custom action for a 223 once, had straight flutes that were too big, it would lock the action when the 223 round slipped into the flute.

The flutes are to cut weight. Straight flutes are shorter so less weight is cut. This is what I was told anyway.