reechloader
that included so many improvements as to be revolutionary. This gun
was rifled with a large number of grooves and fired lead-coated
projectiles. Much of its success, however, was due to the built-up
construction: hoops were shrunk on over the tube, with the fibers of
the metal running in the directions most suitable for strength.
Several United States muzzle-loading rifles of built-up construction
were produced about the same time as the Armstrong and included the
Chambers (1849), the Treadwell (1855), and the well-known Parrott of
1861 (figs. 12e and 13).

The German Krupp rifle had an especially successful breech mechanism.
It was not a built-up gun, but depended on superior crucible steel for
its strength. Cast steel had been tried as a gunmetal during the
sixteenth and seventeenth centuries, but metallurgical knowledge of
the early days could not produce sound castings. Steel was also used
in other mid-nineteenth century rifles, such as the United States
Wiard gun and the British Blakely, with its swollen, cast-iron breech
hoop. Fort Pulaski National Monument, near Savannah, Ga., has a fine
example of a 24-pounder Blakely used by the Confederates in the 1862
defense of the fort.

[Illustration: Figure 12--DEVELOPMENT OF RIFLE PROJECTILES
(1840-1900). a--Cavelli type, b--Whitworth, c--James, d--Hotchkiss,
e--Parrott, f--Copper rotating band type. (Not to scale.)]

The United States began intensive experimentation with rifled cannon
late in the 1850's, and a few rifled pieces were made by the South
Boston Iron Foundry and also by the West Point Foundry at Cold Spring,
N. Y. The first appearance of rifles in any quantity, however, was
near the outset of the 1861 hostilities, when the Federal artillery
was equipped with 300 wrought-iron 3-inch guns (fig. 14e). This
"12-pounder," which fired a 10-pound projectile, was made by wrapping
sheets of boiler iron around a mandrel. The cylinder thus formed was
heated and passed through the rolls for welding, then cooled, bored,
turned, and rifled. It remained in service until about 1900. Another
rifle giving good results was the cast-iron 4-1/2-inch siege gun. This
piece was cast solid, then bored, turned, and rifled. Uncertainty of
strength, a characteristic of cast iron, caused its later abandonment.

[Illustration: Figure 13--PARROTT 10-POUNDER RIFLE (1864).]

The United States rifle that was most effective in siege work was the
invention of Robert P. Parrot