I am not sure about every corpse run. If one does not have Megingjord when one dies, one's max weight for corpse runs is 300. If one does have Megingjord equipped when one dies, one's corpse run max weight is 450.

If Chaos Lord did not have Meginigjord or was not on a Megingjord-related corpse run, max weight should have been 300. Perhaps Chaos Lord will let us know.