Can't recall any accounts, but I'm sure there's a spec list for the various marks of power armor somewhere out there. They should include weights.
Also as an add on thought I'm sure this is techno heresy in the 41st, but a tech priest should be able to remove servos, the backpack and other non-vital systems to lighten standard power armor to the point it could be worn by astartes as standard armor. Would be less taboo in 30k. Useful in prolonged conflicts with units cut off from supply chains.
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