The biggest load I've swallowed by accumilating in one sitting was doing American Bukkake #19. Lots of swallowing happened in the acts of cum swapping and licking it off Fiona Cheeks mouth.
Biggest load by one person would have to be the love of my life (hehe). Of course we dont do it everyday like most porno men so he tends to have the largest load of 'em all.
I've noticed from my experience in the adult biz that Ben English cums a shit load and Dave Hardman as well. When I worked with him he came twice.