nd, and _free from cracks,
seams, and other defects_[1].

[1] _Italics_ are those of the author and refer to defects which
it is the object of his design and method of manufacture to
remedy.

The base plugs must be of forged steel, annealed after forging or
tempering, free from seams, cracks, and other defects, and have the
following physical properties:

Elastic limit 50,000 to 60,000 pounds
Tensile strength 90,000 to 100,000 "
Elongation 18 per cent.
Contraction 25 " "

The projectiles shall be machine-finished, before treatment, as close
to the prescribed dimensions as may be consistent with that operation,
and must, if necessary, be finally finished to the prescribed
dimensions within the allowed variations.

Cylindrical tensile-test specimens with diameter of stem of 0.505 inch
will be used in all cases when the piece is sufficiently thick to
finish the stem to that dimension; when not, the inspectors will
determine the exact form or diameter of the specimens to be used, the
largest practicable being used, considering the piece under test. A
length of stem between gauge marks of 2 inches will be used in all
cases where the elongation is to be taken.

CAPPING

(Art. 21, O. D., U.S.A.)

All steel projectiles shall be fitted, when required, with a cap of
soft steel placed upon the point,[2] the caps to be of the dimensions
shown on the approved drawings and secured in a manner satisfactory to
the Chief of Ordnance by means of a groove, to be turned on the head of
the projectile prior to tempering.

[2] See Frontispiece.

The steel for the cap must show a tensile strength not to exceed 60,000
pounds per square inch, an elongation after rupture of not less than 30
per cent, and a reduction in area of not less than 45 per cent on
standard specimens, 2 inches long between measuring points and 0.505
inch in diameter. These caps will be thoroughly annealed before being
placed upon the projectiles and will be free from cracks and all other
defects.

TEST FOR DETECTION OF HOLES, CRACKS, ETC.

(Art. 27, O. D., U.S.A.)

After the submission of a lot to the inspector for selection of samples
for ballistic test, and before final delivery, the projectiles must be
subjected to an interior hydraulic pressure of 500 pounds per square
inch for one minute. All projectiles in which _holes_, _cracks_, _or
any un