I remember the .577/500 magnum at Larkins. I actually did an enquiry regarding that very rifle. That was a nice backaction hammerless rifle called "climax". That´s the kindI really want and I was close to hear if they wanted my 10bore Manton in a swap. I was simply too slow.I too later did noticed it was gone from their home page. Larkins was kind to send me a few pictures that didn´t showed up on their homepage.
The .577/500 Magnum never reached the level of "full nitro" but only "nfb" which is good enough for me. If I am to have a hammer rifle it must be with steel barrels proved after 1887 with rebounding low profile hammers and 26-27" barrels.

I have though of a few times to have my Rigby 12bore B&S gun to have an x-tra set of new steel barrels done regulated for the 500 grain Woodleigh .50ex bullet doing some 1900-2000 ft/sec which be no problem in a 577/500 h&H Magnum.