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|  MIL-P-70679 (AR)
4.4.3 Testing.
4.4.3.1 Mechanical properties.
4.4.3.1.1 Hardness test. Projectile shall be hardness tested
to confirm uniformity of the heat treatment/stress relief
operations and for the purpose of selecting the projectiles used
for the tensile test. The first twenty-five (25) projectile
bodies minimum, from the first heat treatment batch from one mill
heat of steel (see 4.4.1.1) shall be subjected to this test. The
hardest and softest projectiles from this group tested in
accordance with 4.4.5.1.1 shall be sectioned for tensile testing.
Projectiles from subsequent heat treatment batches (from the same
mill heat of steel) shall use the same hardness range if the same
time, temperature and process parameters are followed. Heat
treatment batches whose parameters have deviated from established
parameters shall require tensile tests of the hardest and softest
from 25 deviating bodies as above. After the 25 are tested,
testing shall be at the rate of 5 per hour. If the hardest or
softest projectile from the group of 25 fails to meet the minimum
tensile strength or elongation requirement, or if during the 5 per
hour screening a harder than the hardest or softer than the
softest projectile fails as above, then 100% hardness testing of
the applicable heat treatment batch is required.
4.4.3.1.2 Tension test From the hardest and softest of the
25 projectiles submitted in accordance with 4.4.3.1.1, two tensile
specimens shall be manufactured from each body, four total. When
it has been determined that the applicable requirements for
tensile strength and elongation have been met, the acceptable
range for hardness shall be considered established for projectile
batches from one mill heat of steel produced in accordance with
4.4.1.1. Should projectiles be found subsequently with a higher
or lower hardness than in the established range, then a new set of
tension test specimens must be prepared and tested in order to
extend the acceptable hardness range. If the heat treatment or
stress relief conditions of a batch have varied from designated
process parameters, a separate set of tensile specimens for that
batch shall be fabricated and hardness tests conducted as above.
After projectiles from the segregated batch are qualified they may
be combined with normal batches in a projectile lot (see 4.4.1.2).
4.4.3.2 Magnetic particle inspection. Testing shall be as
specified in 4.4.5.2.1. After stress relief, hydrotesting and
finish machining, bodies shall be inspected by magnetic particle
inspection techniques approved by the responsible technical agency
according to the following sequence:
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