I had two of the 1873s many years ago. One was a rifle in 38-40. Nice, but it blew the cartridge shoulder forward about 3/16 of an inch and split all the casings. That was in 1969 and you can imagine what those shells cost!
Then I read that the 38-40 was bored deep on purpose to split the case so you could not reload.
The second was a rusted 44-40 carbine found chinked inside the walls of an old log cabin being torn down. I always wondered why that gun was hidden in such a manner!
I wish I still had both of them as the 1873 is still the most snazzy rifle I have ever seen!
Why Winchester went from the steel curved buttplate to the ugly shotgun style in later 1894s is something I will never understand.
On high power rifles like the 1886....curved butts deliver more of a kick than the flat shotgun style. . Did you slug the bore? Perhaps your 38 WCF was really a 44WCF. (Sometimes people interchange the brass lifter which sometimes has the caliber embossed in it.)