I checked out Råneå, but it turns out the Långsund (and also Mörön) I was looking for was in fact in Nederluleå. I thought I had looked through Nederluleå 1806-1820 carefully, page by page. But, there are two pages for Mörön, page 211 and 220 of the Nederluleå household records A I/6b (1806-1820). I will blame my old eyes for the miss first time around. At the bottom of page 220 was a group of people listed as in Långsund with a note on the facing page mentioning a Lars Nordström on page 211. Since I was looking for a Nordström, I went to 211 and there was Lars, in the family I was looking for.
So, I consider this question answered. Thanks for bearing with me.