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Classification of characteristics |
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| MIL-C-18757/5A(OS)
4.3 Classification of characteristics. The characteristics verified by the tests and examinations
specified herein and in the detail inspection are classified as critical, major or minor in accordance with
DOD-STD-2101. Requirements for critical characteristics are identified by the symbol (C), and major
characteristics by the symbol (M). The number following the classification symbol indicates the serial
number of the characteristic. Requirements which are not annotated with a classification code are
classified as minor.
4.4 First article inspection. The first article sample shall consist of 158 cartridge cases and shall be
examined and tested in accordance with table I of MIL-C-18757. The cartridge cases shall be the same
as for regular production and manufactured under the same conditions as the production lot. Further
production of cartridge cases by the contractor, prior to the approval of the first article, shall be at the
contractor's risk.
4.4.1 First article sample acceptance/rejection. Acceptance or rejection of the first article sample
shall be in accordance with table I of MIL-C-18757. For those where the acceptance criteria is not
shown, any failure to meet the requirements shall be cause for rejection of the sample.
4.5 Quality conformance inspection. Quality conformance inspection shall consist of all the
examinations and tests as specified in table I of MIL-C-18757.
4.5.1 Lot size. Unless otherwise specified in the contract or purchase order (see 6.2), the production
lot shall consist of 5000 cartridge cases plus those required for test purposes.
4.6 Methods of inspection.
4.6.1 Visual and dimensional examination. The charges shall be visually and dimensionally
examined for conformance to requirements of 3.2 and 3.9. Four power (4X) magnification may be used
for examination of defects.
4.6.2 High stress expansion test. Each cartridge case in the lot (see 4.5.1), after heat treatment but
prior to tapering, shall be subjected to a high stress expansion test. The cartridge case shall be expanded
diametrically 0.050 inch minimum while under pressure, in a zone extending from 1.5 inches above the
flange to 9 inches above the flange. Expansion will decrease as the flange is approached with expansion
at the flange to be zero.
4.6.3 Hardness. Hardness testing shall be as specified in MIL-C-18757. Hardness readings shall be
taken on each of two sections cut longitudinally from diametrically opposite quadrants of each cartridge
case.
4.6.4 Elongation test. Circumferential specimens cut from three positions shown in figure 1 shall be
tested for elongation in accordance with MIL-C-18757.
4.6.5 Tension test. Circumferential specimens cut from three positions shown in figure 1 shall be
tested for yield strength in accordance with ASTM E8. An offset value of 0.002 inch per inch length
shall be used to determine yield strength.
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