Conjecture is just conjecture and if unsupported by facts it is
misleading.

A review here and on 470 Mbogo.com suggests the 650 gr 577 light lacks penetration on Ele at difficult angles. Whether the 750 gr solid compensates for this at 200 fps less than the full 577 NE is unknown.Perhaps others here could enlighten me regarding its performance and penetration on Ele.

http://www.470mbogo.com/BigBoreCompendium/

In any event the penetration of the 500 NE is not in doubt and is great!! No flies on this cartridge!

http://www.470mbogo.com/BigBores/BigBores7.html