MIL-DTL-13931J
4.5.3 Shop and serial numbers. Where shop numbers are assigned, inspection records shall identify
which shop numbers are assembled with the item serial number (3.4.7.6.5).
4.5.4 Chromium plating inspection. The chromium plating process including the cleaning prior to
plating, reverse etch cycle, plating cycle and thermal treatment after plating, time and treatment at the
temperature specified on the applicable drawing, shall be certified by the contractor or heat treating
facility and made available for the Government representative upon request.
4.5.5 Welding. Welds shall be examined for completeness, appearance and conformance to fielding
requirements specified on the applicable drawing.
4.5.6 Assembled items. Assembled items shall be inspected, functioned and tested as provided for in the
applicable individual cannon specification. If any defective parts are found they shall be replaced with
conforming parts and segregated for disposition. Each assembled item shall be visually examined for
completeness of assembly; for verification of markings, including serial numbers, weight, center of
gravity, quarter lines and model designation; for freedom from chips, dirt and foreign matter; and for
compliance with workmanship requirements.
4.5.7 Autofrettage. The autofrettage (see 6.3.7) process shall be under the surveillance of the
Government representative. The Government representative shall observe any detail or operation and
verify any measurement at any stage of the operation that is deemed necessary. From test results
furnished by the tube forging contractor, the lowest yield strength test value obtained at the breech end of
the tube shall be used to determine the required minimum bore enlargement in accordance with the table
on the applicable drawing.
4.5.7.1 Before autofrettage. After machining is completed in preparation for autofrettage, the bore
diameters of each tube shall be measured with approved inspection equipment. The measurements shall
be recorded and identified with each tube.
4.5.7.2 After autofrettage. After autofrettage, bore diameters of each tube shall be measured with
approved inspection equipment. The measurements shall be recorded and identified with the individual
tube.
4.5.7.3 Tube bore enlargement. The actual bore enlargement of each tube shall be calculated from the
measurements of the bore diameters before and after autofrettage. The calculations shall be recorded and
identified with the individual tube. Any tube not having the minimum bore enlargement or having an
enlarged bore diameter exceeding the maximum bore diameter permissible shall be rejected.
4.5.7.4 Material soundness of autofrettaged tubes. The interior surfaces of each autofrettaged tube shall
be borescoped and the exterior surfaces shall be magnetic-particle inspected in accordance with the
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