It looks like those guys do have a patent (http://www.freepatentsonline.com/6324780.html).
What this means is that no other manufacturer can utilize this same, or substantially similar technique, to spiral flute a barrel, and MAKE MONEY from the service. Thus, you could spiral flute your own barrel, you just couldn't offer the service to anyone else, since that would violate the patent that Shaw holds.
You could do the following: In their patent, they claim "For example, if the gun barrel 10 has spiral flutes that are twenty percent longer than straight flutes for the same length of a gun barrel then it is believed that the spiral fluted gun barrel will cool twenty percent faster than the straight fluted gun barrel. Further, it is believed that the stiffness characteristics will improve with the spiral fluted gun barrel over a straight fluted gun barrel."
The supreme court recently held that you could "try out" patent to see if their claims are valid. So you could get someone to spiral flute a barrel for the purposes of seeing if this method allows the barrel to cool faster, or is actually stiffer. If it turns out that spiral fluting is merely cosmetic, and offers no real advantages over existing prior art, you could then challenge the patent.