I don't know very much about the Remington hybrid rifles, except that the .45-70 Remington-Keene was well before 1900, and I thought the Remington-Lee was a US Navy WWI (not WWII) rifle, chambered in 6mm Lee only
.
The 6mm Lee Navy rifle was a straight pull built by Winchester. That's what you are thinking of. Some were on board the U.S.S. Maine when it was sunk in Havana Harbor in 1898. These were later salvaged and sold by Francis Bannerman, and are known by a list of specific serial numbers.
The Remington-Keene was a tube-fed bolt action gun used in small quantities by the U.S. in the 1880s.
Remington built a number of turn bolt rifles designed by James P. Lee, specifically the U.S. Navy Models 1879 and 1885, the U.S. Army Model 1882, and the Model 1899 which was never used by any American Armed Forces, but was used by a number of other countries.
These were all detachable magazine fed rifles and were the precursors of the Lee-Enfields we all know and love. If you ever see one, the family resemblance is obvious. (BTW, James P. Lee is generally credited with the invention of the detachable box magazine, just as John M. Browning is credited with inventing the operation slide on auto pistols.)
The Model 1899 was made in many different calibres and sold both as a military type rife and in sporter versions, as well. The Michigan State Militia purchased about 1000 of the Model 1899s in .30-40, and it was also sold throughout South America in 7mm Mauser.
Sporter versions of the Remington-Lee were chambered in .30-40, .30-30, 6mm Navy, 7mm Mauser, .38-55 and a host of others and were produced into the early 20th century.
