Some dark corners of the webway refer to the glory days of the "Third Edition Paradigm" (3rd - 7th editions) as "midhammer" 40,000 to differentiate from "oldhammer" (Rouge Trader and Second Edition) and the current editions.
With our Third Xhorik War campaign using 4th Edition rules and our upcoming Rynn's World campaign also planning to use that ruleset, I wanted to document when the various rules and supplements were released in order to help determine which rules are most appropriate.
The books we have are in normal text; those we do not are in grey. The books we are using will be in bold red.
Third Edition Rules: October 1998
Codex Space Marines (3rd): 1998
Codex Blood Angels (3rd): 1999
Codex Imperial Guard (3rd): 1999
Codex Eldar (3rd): 1999
Codex Assassins (3rd): 1999
Codex Orks (3rd): 1999
Codex Armageddon: 1999
Codex Tyranids (3rd): 2001
Codex Chaos Space Marines (3.5th): 2002
Codex Imperial Guard (3.5th): 2003
Codex Witch Hunters (3rd): April 2004
Fourth Edition Rules: August 2004
Codex Space Marines (4th): 2004
Codex Tyranids (4th): 2005
IA3 Taros Campaign: October 2005
Cities of Death: June 2006
IA4 The Anphelion Project: December 2006
Apocalypse: October 2007
Codex Orks (4th): January 2008
Fifth Edition Rules: July 2008
Codex Space Marines (5th): October 2008
Codex Imperial Guard (5th): May 2009
Codex Planetstrike: 2009
IA8 Raid on Kastorel-Novem: May 2010
Battle Missions Scenarios Book: 2010
IA9 Badab War Part 1: October 2010
IA10 Badab War Part 2: January 2011
Sixth Edition Rules: June 2012
Codex Space Marines (6th): September 2013
IA3 Taros Campaign (2nd Edition): October 2013
Seventh Edition Rules: May 2014
Codex Orks (7th): June 2014
Codex Space Marines (7th): June 2015
