Ok I found some weights:

http://www.thecrosbygroup.com/produc...g/body_190.htm

5/16" chain is ~1.1lbs/ft (110lbs/100ft)

5/8" chain is ~3.78lbs/ft (378lbs/100ft)

I know this isn't the 4x-5x that I claimed but I forgot to take into acount that as the individual links get longer it takes less links to make X length so that reduces your total weight by a factor.

Anyways, I hope this helps. I'm looking for a retail source for you.

IronWorker