Sinclair has a minimal website: http://www.sinclairintl.com/
The phone number is listed on the page.
Neck turning is essential with the precision chambers in my bench rifles, but it has resulted in minimal gain in group size with all but one of my factory varmint rifles. It isn't a bad idea, particularily if you limit yourself to 80% or so clean up, just be pleasantly surprised if you see a big improvement for a fair amount of effort.
If you are inclined to try this, check out Sinclairs' setup for neck turning using a power screwdriver. They also sell a jig that makes tool setup a breeze. I no longer bother to use a lathe for most neck turning; this outfit gives excelent results..
[This message has been edited by bfoster (edited July 10, 2000).]