There's a guy in Hungary who collects airgun pellets and builds a database from the photos of pellets. He makes professional macro photos about each sort of pellets and publishes weight and length datas as well: You can find the database here: Loksi's Pellet Picture Database If anyone has got a kind of pellets which aren't listed on his website yet and would like to help him to expand the database, please contact him: Zoltan Vass, http://www.loksi67.com/index_2.htm
there's also this one as well http://www.photosbykev.com/wordpress/2009/01/20/air-rifle-pellet-database/