@MiK - Essentially. For a time they were suggesting 6.44mm, 0.58g BB's were the future of sniping. You'd also need to buy a specific barrel etc from them as part of a kit of course. As far as I can see, the idea didn't catch on at all and hasn't even been mentioned by them since.
20+ years ago Marushin and a few other manufacturers made stuff in 8mm, they've been around for a while and judging by how many bb manufacturers make 8mm bbs, you can guess how well it went