Those "flutes" Lon a so called "rifled" slug are for show. They do not catch the wind and spin as they travel down range. I have a couple of slug moulds which do not have the flutes and those slugs shoot as well as the factory ones.
I'm pretty sure those slugs will "pattern" but how well they will group is up to the individual gun and slug. In the larger bores I have found one brand to work better in a particular gun while a different brand of slug may work better in a different gun of the same bore size. One can only buy a mixture of slugs and try them. Then go back and buy more of the one that did the best - if any can be found.
