Just a few articles regarding problems with the 500 gr 458 at 1900+ with Ele and the marked improvement with the 458 Lott et al--Some of this is due to case capacity/bullet quality but note 1900+ fps only penetrated one half as deep as others 200fps faster.

http://www.cybertorpedo.com/africanhunter/classcart/458_watts_lott_01.htm

http://www.african-hunter.com/WhatsWrong.htm

http://www.cybertorpedo.com/africanhunter/firearms/solids_monometals_04.htm

If this is so then how would a 540 gr at 1550 fps(much,much slower) possibly hold its own??