It seemed like a great idea...
I finally got around to try my "propeller head" sleeve-slug design. The idea was that the "fins" on the nose would cause the slug to rotate during flight, thereby increasing accuracy. That was the plan anyway, but even if it didn't improved accuracy, the slugs should still shoot as well as a more traditional nose design - or so I thought...
http://i1370.photobucket.com/albums/...psnuivujxz.jpg
The five shot group at the right side of the target is almost five inches. Not very impressive since the range was only 30 meters. I had five more with a different type of plastic (HDPE) and hoping for a better result I started on the left target. The first two shots landed four inches apart and since you don't have to empty the whole bottle to discover the milk is sour, I decided to quit.
I had brought along three rounds of a previous sleeve-slug - same load, same sleeve, but a more traditional nose design. I shot them for comparison at the center target and got a nice two inch group! Of course, it could be a fluke, but I will do some more testing at different ranges.
As for the propeller head design, it is dead and buried!