As the fluff goes after the Horus Heresy the space marine chapters were reduced to @ 1000 men and each chapter had 10 companies of 100 each, as proscribed in the Codex Astartes penned by Roboute Guillman. The most notable exception to this being the Space Wolves who have twelve Great Companies, that are not restricted to 100 men each. The Space Wolves have a thirteenth Great Company that made it\'s reappearance during the recent Abadon\'s Thirteenth Black Crusade, the Wulfen Company. the Space Wolves also have a succesor chapter, The Wolf Brothers, but I believe the Wolf Brothers were unsuccesful and ended due to genetic instability. As of the most recent writing, Space Marine Codex, the Salamanders have no known succesor chapters. That doesn\'t mean there aren\'t any, just means they aren\'t known. Gives the creative person the ability to create another chapter in their own colors and and model it after the Salamanders for game play. There are cases of entire space marine chapters being decimated during a campaign and not being able to perpetuate because gene seed was lost or not able to be harvested. This could be easily used to explain the no known succesor chapters line. The Firehawks I believe were a Cursed Founding Chapter, and the whole chapter was lost during a warp jump. The rumor is they return as the Leagion of The Damned.
Hope that helps....
