Originally Posted by Angel of Blood
So you mean during the Great Crusade or 40k? Because 40k both are pretty adherent to the codex and number the standard 1000. The Blood Angels were listed as 100,000 strong in Fear to Tread. Not certain, but fairly sure the White Scars are fairly average, 80,000 - 100,000 range.
Great Crusade, of course. See the Forge World mention. And I think Vth Legion has to be rather large(I personally conjecture between 150,000 to 200,000), just similar way as the Alpha Legion, especially considering this intriguing tidbit...
Documentary evidence attests that the IVth Legion gene-seed showed an above-average adaptability and rates of implant rejection were notably low, particularly in comparison with difficulties in large scale implantation encountered with other Progenoid types, which would not be eliminated until the acquisition of the gene-labs of Luna. This advantage meant that the IVth Legion's fighting strength was built rapidly, expanding to several fully battle-ready battalions in size while some of the other nascent Legions were still yet unable to field more than an active century. This in turn meant that the IVth Legion was very swiftly put to active-service alongside the Ist and Vth Legions.
Also, as fare as I know, "fairly average" Legion size means 100,000 to 130,000. And above 150,000 is deemed as "mid-high" range, whilst 80,000 to 100,000 is definitely below average to the smallest.
Finally, I guess it is very probable that Dark Angels are one of largest, if not largest, Legions, even after infamous Rangdan Xenocide.
I thought the BAs were 120,000 and knocked down to 100,000 after the Traitor's trap?
I speculate it can be very much reshuffled in the next Forge World installment. Because that 120,000 number seems, apparently, did not include or reckon other handful of Blood Angels elements and detachments spread(or stranded) across galaxy after all.