In the 1880's. the U.S. began looking for a 
replacement for the .45-70 Government cartridge.  
In 1892, it introduced the .30-40 Krag with the 
new Krag-Jorgensen bolt-action rifle.
 
    The .30-40 Krag was limited to a chamber 
pressure of 40,000 c.u.p., over 20% below that of 
the .308 Winchester, which shares the same case 
powder capacity.  Because the .308's chamber 
pressures may exceed 50,000 c.u.p, the same 
powder volume may house like amounts of 
slower-burning magnum-type powders, yielding a 
300-400 fps edge with a 150-grain bullet.

    In 1903, the .30-40 was replaced by the 
.30-03, which had ballistics at or above the 
.308, but required a larger case to achieve it.  
Three years later, the .30-03 begat the legendary 
.30-06.

    The .30-40 held great interest in the 
civilian market.  The DCM made surplus Krag 
rifles readily available in the 1920's, and it's 
ballistics are quite adequate for up to deer-size 
game.  To be certain, it's heyday has passed, as 
they are rarely encountered "in the woods" 
anymore, but are frequently seen at gun shows.