Where 577/500 Hartmann & Weiss and 577/500 N°2 Nitro Express appear, according to Westley Richards, to be the same cartridges.

"The .577/.500 No2 calibre in nitro format was a cartridge introduced by Hartman and Weiss who made some single shot falling block rifles in this calibre. The original cartridge was a black powder version which was introduced sometime before 1879 this was then developed in various formats including Nitro for black and fullNitro load with a variation in bullet weight of from 300 grains up to 570 grn, The nitro version for our rifle used the 570 grn. bullet and we think the velocity was around 2300 fps. It was a powerful round and the rifles weight of 14 lbs. compensated for this."