Military Cartridge Section
.50 Remington Army Revolver (M71)
The .50 Remington a/k/a .50 Remington Army (M71) revolver cartridge  was the second version of this caliber.
The first version: .50 Remington Navy (M67) was introduced in the U.S.A., around 1866 for the Navy Model 1867
(M67) and was a straight, with very slight taper, rim-fired cartridge and later as a straight walled center-fire case.
The later version (below) .50 Remington (M71) Army was a “bottle necked” case for the Remington Army Model
1871 rolling block pistol introduced in 1870 had an “Inside Primed” Benet Cup internal primed center-fired cartridge.
Then later, sometime around 1873, the cartridge primer changed to an external primed (Martin Primed) and later to a
regular, more modern, outside primed case.   
Ammunition was loaded by both Remington and Winchester and was available until about 1920, making this caliber
obsolete for over 96 years on regular primed and up to 146 years on inside primed at this writing.
The Army (M71) verision has a large diameter projectile and will not fire in the Navy (M67) revolver.
Below .50 Remington (M-71) Army Revolver Cartridge
Benet Inside Primed
.50 Remington (M71) Army
revolver cartridge produced
by Frankford Arsenal, 1872
production. (145 years old)
Internal "Benet Cup"
experimental primer only
made for 2 years before
changing to  a "Martin
external primer".
Note the 2 machined crimps
outside the case that hold
the internal primer in place