The market has been rocky with bad economic news out of Europe and a weak jobs report in the U.S., but its been a smooth ride for all-terrain and other recreational vehicle makers -- as well as gun maker Sturm, Ruger & Co.'s (RGR), whose stock rose 4.2% to 51.59 as of early afternoon Thursday. ATV maker Polaris (PII) gained 4.1% to 73.10. The company was No. 42 on this week's IBD 50 list, and with Sturm-Ruger leads IBD's Leisure-Products group with