BR: Yep I agree. Remembering that this is a tool to be used is key to endvor. Finding the correct gear to facilitate it is another adventure to be enjoyed.  Don
There a lot of misinformation out there on the 44-90 so the only proof we have is the actual rifle that it was used in. Also many modifications have taken place in the last 135 years. So forming an opinion should be based of factual examples. Cartridges sometimes have been fired in incorrect chambers leading to all sorts of speculation. Also theres been gun "specialists" forever.
 In my humble opinion:
1. first of these was a 44-60
2 secondly along came the 44-77 with greater case capacity, named also 43 Spanish, note the specks, then it was loaded with 90 grains 
3. third a longer case was used to accomodate the want for greater case capacity, ie 90 grains so now there was an "official" 44-90 2 5/8
4. fourthly most rifles were made, at the time(1869) for govt. contracts, all over the world, so to accomodate, note name changes with the same specs.(or darn close)(companies were well aware of proprietary cartridges and if you owned a Remington they wanted you to shoot remington cartridges same with Sharps) Winchester and Marlin got into it in court big time...
Remington and Sharps worked somewhat together to create  long range rifles to compete at Creedmore for 1873. The 44-77 was developed somewhat before the Mod. 69 Sharps so all this may have origionated from Sharps. ( had to be developed before being adopted, 1868????) By 1874 the 44-90 was fully developed and used extensively.
I am just curious if this all was not of Russian invention and picked up by western countries...
Don  rustyrelx
PS its a great cartridge not to be overlooked by any others IMHO