The Remington-Keene reifle was the brainchild of one James Keene of Newark, NJ, who began patenting its features in 1874. The gun would eventually go into production with the Remington company in 1877 and remain available until 1888, selling a total of about 5,000 copies.
The Remington-Keene rifle/carbine was submitted to government trials, as were so many other repeating rifles of the period. Keene’s design, however, had a number of features that one would have expected to endear it with Army ordnance officers. Despite being a bolt action, Keene place a large and unmistakeable hammer on the end of the bolt – something that would make military users much more comfortable with the design. In addition, to mollify some of the ordnance department’s safety concerns the striker on the Keene only resets to half-cock when the bolt is operated. The shooter must manually cock the striker (which looks like a hammer) before firing. Another clever feature of the Keene design was that its tube magazine could be loaded either through the top with the bolt open, or from below with the bolt closed.
Locking on the Keene was performed by a single large lug, which also functioned as the bolt handle. Unlike other rifles with similar shell lifters, the Keene system held the cartridge in control while on the elevator, avoiding the potential problem of a cartridge falling out mid-loading – which was possible in rifles like the Lebel and Kropatschek.
The Navy did purchase 250 Remington-Keene rifles for use on on the USS Michigan and USS Trenton, and the Indian Bureau also purchased several hundred for its Indian agents. These guns were all chambered fort he standard .45-70-405 cartridge, but commercial guns were also available in .40-60 and .43 Spanish calibers. Magazine capacity was 9 cartridges in a 29 1/4″ rifle and less in the shorter carbine models (I haven’t found reliable numbers for the specific carbine capacity).
Despite its creative elements, the Remington-Keene was pretty thoroughly inferior to the Lee rifle designs the Remington was also producing, and they let production come to an end in the late 1880 in favor of Lee rifles.