12951019 Drawing

1/ Failure of the sample, unless otherwise specified in the applicable test method, to meet the requirements shall cause rejection of the represented lot.

2/ Failure of one carbine in the sample of thirty-two to meet the requirements shall cause a second sample to be tested from the same lot. The second sample shall consist of thirty-two carbines, exclusive of the first thirty-two, (cumulative, sixty-four carbines). Failure of two or more carbines in the first sample or the combined first and second sample shall be cause for rejection of the represented lot.

3/ The 30 round magazines selected for the endurance test shall be visually and manually inspected by the contractor for workmanship and completeness of assembly and determined to be satisfactory prior to test.

4/ The sample shall be selected from each inspection lot of repair parts.

5/ when carbines are produced concurrently by more then one manufacturer, each manufacturer shall forward five carbines monthly (see 6.2) for the interplant interchangeability test. The contractor will be informed of any failure of the carbines to meet the prescribed requirements.

6/ when five successive inspection lots meet the requirements, the inspection lot size shall be increased to 5000 carbines or a month's production, whichever is smaller, and the inspection sample selected. If rejection of the inspection sample occurs at any time, the inspection lot size of 1,000 carbines (or smaller) shall be reinstated and the above procedure repeated in returning to the 5000 carbine (or smaller) lot size.

4.5.3.2 Component parts and concurrent repair parts testing. Raw material testing, part testing, and certification shall be in accordance with the criteria specified in the contract (see 6.2). This will include chemical analysis and physical tests of materials, and tests of protective finish, heat treatment, and function of parts as applicable. The contractor shall accomplish these tests prior to assembly of component parts into the end item and acceptance as concurrent repair parts.

4.5.3.3 Packaging testing.

4.5.3.3.1.1 Materials. The contractor shall have available for review by the Government representative a statement of findings that the packaging materials conform to the applicable Special Packaging Instructions and specifications.

4.5.3.3.1.2 Determination of cleanliness testing. The contractor shall test items from each inspection lot for determination of cleanliness using the test method specified in 4.7.9.1. Sampling shall be in accordance with MIL-P-116.

4.5.3.3.2 Repair parts. Testing of packaging of repair parts shall be performed in accordance with the criteria specified in the contract (see 6.2).

4.6 Inspection egulpment. The inspection equipment required to perform the inspections specified herein is identified in the "Inspection Method" column of the Classification of Defects and in the methods of inspection. Contractor inspection equipment designs shall be submitted for Government approval as specified in the contract. Designs which provide variable measurements instead of attributes data are preferred in order to facilitate the use of statistical process control. The provisions of MIL-A-70625 shall apply to all automated acceptance inspection equipment. See MIL-w-6 3150 and 6.7. Responsibility for acquisition, maintenance, calibration and disposition of all inspection shall be in accordance with MIL-I-45607 and MIL-STD-45662.

4.7 Methods of Inspection.

4.7.1 Headspace test. This test shall be performed during individual carbine testing in accordance with TABLE III using inspection equipment per drawings 8443915 and 8443949.

4.7.1.1 Minimum gage. The bolt shall be moved rearward to the open position. The minimum headspace gage shall be inserted in the chamber and the bolt shall be returned to the battery position. Only finger pressure shall be applied to close the bolt. To be acceptable the bolt shall fully close.

4.7.1.2 Maximum gage. The bolt shall then be retracted to the open position and the minimum headspace gage removed from the chamber. The maximum headspace gage shall be inserted in the chamber and the bolt returned to the battery position. Only finger pressure shall be used to close the bolt. To be acceptable the bolt shall not fully close.

4.7.1.3 Dimensional inspection. If the above results are in dispute, the carbine shall be disassembled and the 1.6206 + .0030 barrel dimension and the .156 - .003 bolt dimension shall be measured to determine compliance with the drawing requirements.

4.7.2 Firing Pin indent test. This test shall be performed during inspection lot testing in accordance with TABLE IV utilizing inspection equipment per drawings B440218, 8440219, 8440220, 8440920 and Government furnished copper compression cylinders for insertion in the barrel chamber.

4.7.2.1 Firing mechanism indent. The carbine shall be held in a vertical position (muzzle down) with the muzzle end supported. The bolt shall be retracted to the rearward position and held open. A zero indicator reading shall be made on the height of the copper pressure cylinder before Insertion into the chamber adapter. The chamber adapter containing the copper compression cylinder shall then be inserted in the barrel chamber. The bolt shall be manually returned to the battery position, the trigger shall be pulled to release the hammer and indent the copper compression cylinder. The chamber adapter shall be removed from the barrel chamber and the depth of the indent on the copper compression cylinder computed by measuring the distance from the original zero indicator reading to the bottom of the firing pin impression. The indent impression shall be visually examined to determine if the concentricity requirement has been met.

4.7.2.2 Bolt action Indent. The bolt shall again be retracted to the open rearward position and held open. A zero indicator reading shall be made on the height of the copper compression cylinder before insertion into the chamber adapter. The chamber adapter containing the copper compression cylinder shall then be inserted in the barrel chamber. The bolt shall be returned to the battery position under spring action. The trigger shall not be pulled. The chamber adapter shall be removed from the barrel chamber and the depth of the indent in the copper compression cylinder computed by measuring the distance from the original zero indicator reading to the bottom of the firing pin impression.

a. Carbine serial number.

b. Inspection lot number.

c. Computed measurement of firing pin indent for both firing mechanism released and not released.

4.7.3 Trigger pull test. This test shall be performed during individual carbine testing in accordance with TABLE III using Government approved inspection equipment.

4.7.3.1 Minimum load. The carbine shall be cocked and the selector lever placed in the "SEMI" position. The minimum load shall be gradually applied to the center of the trigger and exerted in line parallel to the axis of the barrel bore. To be acceptable, the hammer shall not release.

4.7.3.2 Maximum load. The carbine shall be cocked and the maximum load shall be gradually applied to the center of the trigger as before. To be acceptable, the hammer shall release.

4.7.3.3 Creep. The carbine shall also be manually tested to assure that the trigger pull is free of creep (see 3.4.3) and that the trigger returns under spring action to its normal forward position after partial or complete trigger pull.

4.7.4 High-pressure resistance test. This test shall be performed during individual carbine testing in accordance with TABLE III, using a fixture for holding the bolt and barrel assembly per drawing 11837944.

4.7.4.1 Test cartridge. One (1) high-pressure test cartridge (see 3.4.4) shall be fired in each bolt and barrel assembly. Unless otherwise specified, the bolt and barrel assembly shall be tested concurrently. After proof firing, cartridge cases shall be examined for bulges, splits, rings and other defects caused by defective chambers of the barrel assembly.

4.7.4.2 Barrel Inspection. The barrel assembly shall be magnetic particle inspected in accordance with MIL-STD-1949 utilizing a current of 400 to 500 amperes for circular continuous magnetization. The barrel assembly shall be examined for evidence of cracks, seams and other injurious defects.

4.7.4.3 Bolt inspection. The bolt shall be magnetic particle inspected in accordance with MIL-STD-1949 utilizing standard five turn magnetizing coil with a current of 200 to 300 amperes. Both circular and longitudinal continuous magnetization with wet fluorescent solution shall be used. The bolts shall be examined for evidence of cracks, seams and other injurious defects.

4.7.4.4 Proof markings. Proof marks and magnetic particle inspection marks shall be applied on barrel assemblies and bolts that have passed this test.

4.7.5 Function firing test. This test shall be performed during individual carbine testing in accordance with TABLE III, and shall be accomplished with the carbines held in a Government approved firing stand simulating shoulder firing. The ammunition used on this test shall be as specified in 3.4.5, except that the ammunition used in semi-automatic firing shall be as specified in 3.4.6.

4.7.5.1 Lubrication. The carbines shall be prepared for firing using lubricant in accordance with MIL-L-63460 (CLP). Apply a light coat of oil to all surfaces of the disassembled bolt carrier group. Apply one drop of oil in each hole on the right side of the bolt carrier and in the open end of the bolt carrier key. (Do not apply excessive oil in the bolt firing pin recess.) Apply a moderate coat of oil on all firing mechanism components in lower receiver.

4.7.5.2 Pre-flrlng. The carbine shall be given a pre-firing examination to assure that no safety hazard exists.

4.7.5.3 Firing procedure. The selector lever of the carbine shall be set in "SAFE" position and shall be checked to assure that the carbine cannot be fired.

4.7.5.3.1 Automatic firing. The selector lever shall be set on "AUTO" for automatic firingT The carbine shall be fired using a fully loaded 30 round magazine in two (2) bursts of approximately three (3) rounds each, and the remaining rounds fired in a continuous burst. Failure of the carbine to stop firing during the interrupted burst firing upon release of the trigger shall be cause for rejection and recorded as malfunction.

4.7.5.3.2 Cyclic rate of fire- when carbines are required to be tested for cyclic rate of fire, this test shall be conducted in conjunction with the burst firing test of 4.7.5.3.1. The cyclic rate of fire measurement shall be taken on a minimum twenty (20) round continuous burst from a 30 round magazine, while the selector lever is set on "AUTO". The cyclic rate of fire shall be measured using test equipment per drawing 8443572 and shall be recorded.

4.7.5.3.3 Semi-automatic firing. The selector lever shall be set on "SEMI" for semi-automatic firing. Ten rounds shall be fired. The semi-automatic firing shall be accomplished simultaneously with the targeting and accuracy test specified in 4.7.6. During semi-automatic firing, carbines shall be checked to assure that no doubling occurs (i.e., two shots fired with a single trigger pull). Doubling shall be recorded as a malfunction and shall be cause for rejection.

4.7.5.3.4 Manual examination. Manually examine function of magazine catch and visually examine function of bolt catch in assisting magazine ejection. Depressing of magazine catch button shall cause the magazine assembly to be ejected, with spring assist from bolt catch, without binding.

4.7.5.3.5 Malfunctions. Malfunctions that are not attributable to carbines as a result of failure analysis and verified by the Government representative shall not be counted against the carbine; however, such malfunctions shall be recorded.

4.7.5.3.6 Recording of data. The following data shall be recorded:

a. Number of carbines tested and number of carbines rejected per shift.

c. Ammunition lot number.

d. For each carbine that fails, record the following data:

1. Serial number.

2. Type of malfunction or failure (see 6.6).

4. Round number at which failure occurred.

5. Type of firing (semi-automatic or automatic).

6. Round number of magazine at which failure occurred.

7. Type of magazine used (30 round magazine), e. Ammunition defect

1. Carbine in which ammunition defect occurred.

2. Description of defect.

4.7.5.4 Rejected carbines.

4.7.5.4.1 Correction. Carbines rejected because of malfunction or unserviceable part during the test shall be corrected by the contractor and the corrective action shall be recorded. In the event the malfunction cause is classified as Class II or Class III (see 6.6.5), the contractor shall immediately initiate action in accordance with 4.7.5.5.2.1.

4.7.5.4.2 Retest. The carbines shall be retested by firing two (2) thirty round sequences in accordance with 4.7.5.3.1 and the cyclic rate shall be recorded. The carbine shall operate without malfunction or unserviceable parts and shall meet the cyclic rate of fire requirements.

4.7.5.4.3 Second retest. In the event the carbines fail in the retest, the procedure in 4.7.5.4.1 shall be followed. The carbines shall be retested, by firing three (3) thirty round sequences in accordance with 4.7.5.3.1 and 4.7.5.3.3 and the cyclic rate shall be recorded. Carbines shall operate without malfunction or unserviceable parts and shall meet the cyclic rate of fire requirements.

4.7.5.5 Process control criteria.

4.7.5.5.1 Process average. The process average for total carbines tested for function firing during one shift shall not exceed 2.0% defective. This process average for each shift shall be maintained and be available for Government review.

4.7.5.5.2 Failure classification, when the process average exceeds 2.0% defective during one shift, the contractor shall review the failure causes for determination of a seriousness, Class I, II or III malfunction (see 6.6.5). The contractor, in addition, shall provide the government representative with objective evidence of his determination.

4.7.5.5.2.1 Class II or III malfunction, when the malfunction cause is classified as Class II or III, the contractor shall institute corrective action in the manufacturing processes and associated quality control procedures to preclude recurrence of the cause and to assure that all carbines and components containing similar defects are purged from the prime and vendor facilities, when authorized by the Government representative, this corrective action need not include the screening of carbines previously tested for function firing. Upon completion of the preceding, the contractor shall recondition the rejected carbines and retest the carbines as specified in 4.7.5.4.2.

4.7.5.5.2.2 Class I malfunction, when the malfunction is classified as Class I or the malfunction cause cannot be determined, the contractor shall correct the rejected carbines and shall test the first eighty carbines on the following shift by firing two thirty round sequences in accordance with 4.7.5.4.2. when the number of malfunctions occurring during the test of eighty carbines exceeds one, the contractor shall continue function firing acceptance testing in accordance with 4.7.5.4.2 until corrective action has been accomplished to the applicable manufacturing process or quality assurance procedures or both, as evidenced by the testing of eighty consecutive carbines with one or less malfunctions. In the event the malfunction number is one or less during this test, normal function firing testing shall be resumed for all subsequent carbines submitted during this shift.

MIL-C-71186(AR)

4.7.6 Targeting and accuracy test. This test shall be performed simultaneously with the semi-automatic firing of the function firing test (see 4.7.5.3.3) and in accordance with individual carbine test of TABLE III. A Government approved firing stand simulating shoulder firing, and targets in accordance with Figure 1 shall be used. The ammunition used in this test shall be as specified in 3.4.6.

4.7.6.1 Preparation for firing. The front and rear sights shall be set as specified in 3.4.6.

4.7.6.1.1 Warm-up shots. Except for rounds fired during function testing, firing of not more than three (3) warm-up shots off the test target shall be allowed before the carbines are tested for targeting and accuracy.

4.7.6.2 Firing procedure. The selector lever shall be set on "SEMI" and the firing sights shall be aligned on the point of aim specified in Figure 1. Ten rounds shall be fired. The target shall then be checked to determine that the targeting and accuracy requirements have been met (see 3.4.6 and Figure 1). Targets with evidence of a flyer (see 6.6.2) or keyhollng (see 6.6.3) shall be cause for the contractor to repeat the test by firing a ten round complement.

4.7.6.2.1 Sight setting. The optimum sight setting obtained during the targeting and accuracy test shall be maintained on accepted carbines being prepared for shipment.

4.7.6.2.2 Recording data. The following data shall be recorded:

a. Number of carbines tested and number of carbines rejected per shift.

b Test date.

c. Ammunition lot number.

d. Extreme spread of shot group.

e. Reason for retest (flyer and keyhollng).

f. For each carbine that fails, record the following:

1. Serial number.

2. Type of malfunction or failure (see 6.6).

3. Type of magazine (30 round magazine).

4.7.6.3 Rejection. Carbines failing to meet the targeting and accuracy requirement shall be retested by firing a second ten (10) round target, carbines failing to meet the targeting and accuracy requirement on the second target shall be rejected. Rejected carbines shall be corrected by the contractor and the corrective action shall be recorded.

MIL-C-71186(AR)

4.7.6.3.1 Retest. Corrected carbines shall be retested by firing a ten round complement at each of two targets. The targets shall be checked to determine that both targets meet the targeting and accuracy requirements. The rate of fire will be at the contractor's option.

4.7.6.3.2 Rejection. If the retested carbine fails to meet the requirements for both targets, the carbine shall be rejected. If the carbine fails to meet only the accuracy requirements for one of the two targets, a ten round complement shall be fired at a third target. The targets shall be checked to determine that the average of the extreme spreads for the three targets meets the accuracy requirements.

4.7.6.3.3 Second retest. Carbines failing the retest shall again be corrected by the contractor and the corrective action recorded. The carbine shall then be retested by firing a ten round complement at each of three targets. The targets shall be checked to determine that the average of the extreme spreads for three targets meets the accuracy requirements. If the retested carbine fails to meet the requirements for the three targets, the carbine shall be rejected.

4.7.6.4 Process control criteria.

4.7.6.4.1 Process average. The process average for total carbines tested for targeting and accuracy on one shift shall not exceed 6.0% defective for each requirement. If 6.0% is exceeded, the first eighty carbines submitted for testing during the succeeding shift shall be tested for the requirement that exceeded the process limit, by firing a ten round complement at each two targets in accordance with 4.7.6.3.1.

4.7.6.4.2 Increased testing, when the number of failures occurring during the test of eighty carbines exceeds four for either of the requirements, the contractor shall continue targeting and accuracy testing in accordance with 4.7.6.3.1 until corrective action has been accomplished to the applicable manufacturing process and quality assurance procedures as evidenced by testing of 80 consecutive carbines as specified in 4.7.6.3.1 with four or less failures.

4.7.6.4.3 Normal testing. In the event four or less failures occur during the test of eighty carbines, the normal targeting and accuracy testing shall be resumed for all subsequent carbines submitted during the shift.

4.7.7.1.1 Carbines. The interchangeabillty test shall be performed during inspection lot testing in accordance with TABLE IV. Carbines shall be tested for interchange of parts by disassembly and reassembly of parts using parts from a prearranged system specified below. Interchange of parts shall be accomplished by dividing the parts of each carbine into 10 groups of nonmating parts as shown below and distributing the groups into 10 different trays until each tray contains a complete carbine. Groups of parts from carbine number 1 shall be taken in order and placed in trays 1 through 10; groups of parts from carbine number 2 shall be taken in order and placed in trays 2 through 10 to l; groups of parts from carbine number 3 shall be taken in order and placed in trays 3 through 10 to 2, etc. The carbines shall be reassembled using only those parts which are in the same tray. The reassembled carbines shall be tested for headspace, firing pin indent, trigger pull, function firing (including cyclic rate of fire), and accuracy tests specified in methods of inspection 4.7.1, 4.7.2, 4.7.3, 4.7.5 and 4.7.6 respectively. Disposition of interchangeabillty carbines shall be as specified in the contract (see 6.2).

Takedown Pin Detent

(8446585) (2) Receiver, Upper (12972670) **Rear Sight Spring Pin

(MS16562-103) Magazine Catch Spring (8448637) Trigger (8448592) Front Sight Post (9349056) Lock Washer (MS35335-61) **Receiver Extension Nut

(9290020) Buttstock Lock Spring (9 390027)

Barrel and Front Sight Assembly Permanent assembly of: Barrel (9390009), Barrel Extension (9390030), Barrel Indexing Pin (8448551), Front Sight (9349058), Taper Pin (8448575) (2), Handguard Cap (9 390002) Nut Barrel (8448553) Lower Receiver (12972652) Extractor Pin (8448513) Ejection Port Cover Assy

(8448525) Buttstock Lock Pin Nut

(9390026) Sling Swivel (8448571)

Group III

Receiver Extension (9 390019) Bolt (8448510) w/Bolt Rings

(8448511) (3) Ejection Port Cover Pin (8448533)

& Snap Ring (MS16632-3012) Front Sight Detent (844857 3) **Trigger Guard Pivot Pin

(MS16562-129) Trigger Spring (8448593) Takedown Pin (8448584) Magazine Release Button

(8448636) **Spring Pin (MS16562-121) (2) Carrying Handle Assy (12951021)

Group IV

Key & Bolt Carrier Assy

(8448505) Takedown Detent Spring

(8448586) (2) Handguard Slip Ring (8448712) Ejector and Safety Detent Spring

(8448516) (2) Retainer, Buffer (8448582) Trigger and Hammer Pin

(8448609) (2) Front Sight Detent Spring

(8448574) Buttstock Release Lever (9390014) Swivel Mount (12598617)

Group V

Buffer Retainer Spring (8448583) Sliding Buttstock (9390013) Ejection Port Cover Spring

(8448532) **Ejector Pin (MS16562-98) Magazine Catch (8448638) Disconnect (8448635) Plunger Assy (9 349085) Rear Sight Base (12951028) Pistol Grip Screw (AN501D-

416-18) Handguard Spring Assembly (8448555)

Group VI

Rear Sight (9349075) Bolt Cam Pin (8448502) Bolt Catch (8448628) Pistol Grip (9349127) Buffer Assy (9390023) *Pawl Spring Pin (8448521-2) Index Spring (9349069) (2) Handguard Retaining Ring

(MS16626-3137) Elevation Spring (9 349070) Buttstock Lock Pin (9 390025) *Swivel Mount Pin (MS39086-41) (3) Index Spring (12951020)

Ejector (8448515) Rear Sight Spring (12011987) Gas Tube Assy (9390016) Hammer & Hammer Pin

Retainer Assy (8448612) Compensator (9349051) Firing Pin Retaining Pin

(8448504) Catch Plunger (84486 34) Pawl (8448543) **lndex Screw (9349065) Swivel Mount Locking Bar (12598618)

Receiver Pivot Pin (8448621) Firing Pin (8448503) Rear Sight Windage Screw(9349076) **Gas Tube Pin (MS16562-106) Handguard Assy (9390003)

(Top Section) Bolt Catch Spring (8448633) Automatic Sear Pin (8448599) **Compensator Spacer (9 349052)

or Compensator Spacer (9 387 099) & Compensator Shim (9387098) Pawl Detent (8448544) Elevation Index (12951018)

Group IX

Rear Sight Windage Knob

(9349077) Charging Handle Assy

(8448517) **Bolt Catch Pin (M516562-119) Hammer Spring (8448611) Fire Control Selector

(9381367) Bolt Spring (8448542) Elevation Knob (12951019) **Receiver End Plate (9390021) **Buttstock Spring Pin (MS16562-202)

Group X

Extractor (8448512) w/Spring

Assy (8448755) Trigger Guard Assy (8448587) Handguard Assy (9 390003)

(Bottom Section) Automatic Sear Assy (8448595) Action Spring (9390022) Fire Control Selector Detent

(8448631) Plunger Spring (8448540) Rear Sight Ball (MS19060-4Q08) (3)

Disconnect Spring (8448594)

Note: All items preceded by a double asterisk {**) shall be replaced during interchangeability test. Parts inadvertently damaged during interchange may be replaced without penalty when authorized and verified by the government representative witnessing the test.

4.7.7.1.2 Concurrent repair parts. The interchangeability test for concurrent repair parts shall be conducted during inspection lot test in accordance with TABLE IV. The five carbines used for the repair parts interchangeability test shall have met the test requirements of¡TABLE III, firing pin indent test (see 4.7.2) and the classification of defects (see 4.5.2.2.3) shall be disassembled as required and reassembled using the concurrent repair parts. No hand refinement of parts shall be permitted during interchange of parts. A function firing test (including cyclic rate of fire) specified in test method 4.7.5 shall be performed on the reassembled carbines when the following repair parts are interchanged.

(9390007) Extractor Pin (8448513) Disconnect (8448635) Buttstock, Sliding (9390013) Lever, Release (9390014)

(8448637) Trigger (8448592) Bolt (8448510), & remaining parts

Trigger Spring (8448593) Magazine Catch (8448638) Ejector (8448515) Gas Tube Assy (9390016) Bolt Catch Plunger (8448634) Barrel & Front Sight Assy

Compensator (9 349051) Hammer & Hammer Pin Retainer

ASSy (6448612) Ejector & Safety Detent Spring

(8448516) Trigger & Hammer Pin (8448609) (2)

Spring Disconnect (9349116)

Bolt Cam Pin (8448502)

Bolt Catch (8448628)

Buffer Assembly (9390023)

Firing Pin (8448503)

Bolt Catch Spring (844863 3)

Hammer Spring (8448611)

Fire Control Selector (84486 30)

Key (8448506)

Extractor (8448512) w/Spring

ASSy (8448755) Automatic Sear Assy (8448595) Action Spring (9390022) Bolt Carrier (8448507)

4.7.7.2 Interplant. The carbines subjected to interplant Interchangeability test (see TABLE IV) shall be given a preliminary hand functioning to assure proper operation before parts are disassembled from the carbine. The carbines shall be tested for headspace, firing pin indent, trigger pull, functioning and accuracy requirements before and after interchange of parts, using the test methods specified in 4.7.1, 4.7.2, 4.7.3, 4.7.5 and 4.7.6 respectively. Interchange of parts shall be accomplished in a manner similar to that specified in 4.7.7.1.1. Detailed procedures for this test shall be as specified in the contract (see 6.2), depending on the number of different manufacturers involved.

4.7.7.3 Failure of interchangeability test.

4.7.7.3.1.1 Second sample. Failure of parts to reassemble during parts interchange or subsequent failure of any carbine to meet the headspace, firing pin indent, trigger pull, functioning and accuracy requirements shall be cause for selection of an additional sample of carbines from the represented inspection lot to determine the prevalence of a similar defect. The sample shall consist of 20 carbines when the lot size is 1,000 and 50 carbines when the five lot (or larger) group is represented.

4.7.7.3.1.1.1 Acceptance. If a similar defect is not found, the non-conforming carbines shall be corrected and the lot shall be accepted.

4.7.7.3.1.1.2 Rejection. If a similar defect is found, the inspection lot shall be rejected and the contractor shall examine and correct all carbines in the represented lot to insure the material containing the defects or similar defects revealed during testing are purged from the represented lot and are not presented to the Government for acceptance. The contractor shall also correct the applicable production and inspection processes and procedures to prevent the recurrence of defects revealed during the test.

4.7.7.3.1.2 Accuracy failure. Carbines failing to meet the accuracy requirements shall be corrected by the contractor to meet the requirements before they are returned to the represented lot for final acceptance.

4.7.7.3.2 Repair parts. Failure of any repair part to meet the interchangeability requirements shall cause the contractor to determine the cause of failure and inspect a sample representing the lot of parts to determine the prevalence of a similar defect. Sampling shall be in accordance with TABLE II, using Inspection Level I. upon completion of inspection, the lot shall be reconditioned as necessary prior to submitting the lot for retesting. The contractor shall evaluate and correct the applicable production and inspection process and procedures to prevent recurrence of the defects revealed during the testing.

4.7.7.3.3 Recording of data. The following data shall be recorded:

a. Inspection lot number.

b. Carbine serial numbers.

c. All measurements required for headspace, firing pin indent, trigger pull, functioning and accuracy requirements before and after interchange of parts.

d. Cyclic rate of fire before and after interchange of parts.

e. Failure of any part to interchange.

f. Any damaged part that was replaced.

4.7.8 Endurance test. The endurance test shall be performed during inspection lot testing in accordance with TABLE IV. Carbines shall be held in a Government approved firing stand using a Government approved timing gage for measurement of cyclic rate of fire. The ammunition used for this test shall be as specified in 3.4.7.

4.7.8.1 Cleaning and lubrication. Carbines shall be cleaned and lubricated at the beginning of the test and at the end of every 10 cycles. Carbines shall be lubricated after the fifth cycle and every 10 cycle increment. No other cleaning and lubrication shall be performed during this test. At the close of each day's firing, the carbine shall be protected against corrosion.

4.7.8.1.1 Lubrication. Carbines shall have been lubricated using lubricant in accordance with MIL-L-63460 (CLP). Apply a light coat of oil to all surfaces of the disassembled bolt carrier group. (Do not apply excessive oil in the bolt firing pin recess.) Apply a moderate coat of oil on all firing mechanism components in lower receiver.

4.7.8.1.2 Cleaning. Carbines shall be cleaned with a cleaning solvent in accordance with MIL-C-372 and the following procedures:

a- Barrel. Brush bore thoroughly with a brush soaked in cleaning solvent. Brush the bore from the chamber to the muzzle using straight through strokes. Do not reverse direction of brush until it extends beyond the muzzle. Continue brushing until the bore is covered with solvent. Dry the bore by pushing clean dry swabs through the bore. Continue until the swab comes out clean and dry. Clean dry compressed air may be used for preliminary drying.

b. Barrel chamber. Insert the cleaning rod section and chamber brush that has been dipped in cleaning solvent into the chamber and use reciprocating plunge strokes and rotational 360┬░ motions. Dry chamber with cleaning swabs.

c. Barrel extension. Using a small bristle brush that has been dipped in cleaning solvent, clean the locking lugs in the barrel extension. Remove excess cleaning solvent.

d. Bolt carrier group. with the exception of the bolt carrier key, bolt rings, extractor spring and the ejector, disassemble all parts, wash these parts in cleaning solvent and remove all carbon deposits. Particular attention should be given to the areas under the face of the extractor and behind the three rings on the bolt. Clean the bolt carrier key hole with a worn bore brush that has been dipped in cleaning solvent by rotating the brush clockwise (repeat several times until clean). Remove excess solvent and dry.

e. Upper receiver. Clean with cleaning solvent and remove all powder fouling. Clean the protruding gas tube using a bore brush attached to a section of the cleaning rod. Saturate the brush with cleaning solvent. (Do not use any type of abrasive material to clean the gas tube. Remove excess cleaning solvent.)

f. Lower receiver. Remove all carbon residue from lower receiver group assembly using cleaning solvent. Drain excess solvent from lower receiver cavity and dry.

4.7.8.2 Magazine. The twenty (20) 30 round magazines used in each carbine shall be numbered and used in rotation during this test. Magazines shall be fully loaded for each use. Each magazine used during this test shall be cleaned at the specified cleaning interval for the carbine with a cleaning solvent in accordance with MIL-C-372 and blown dry with prepared compressed air.

4.7.8.3 Measurements. The following measurements shall be made during this test:

a. Headspace. Headspace for carbines being fired with 30 round magazines shall be measured and recorded at the beginning of the test and at the completion of the 50th cycle. After the 50th cycle, the headspace shall not be more than .0028 inch greater than the initial measurement and shall not exceed .0024 inch over maximum.

b. Cyclic rate of fire. The cyclic rate of fire for carbines being fired with 30 round magazines shall be measured and recorded during the second magazine of the first cycle and the second magazine of every ninth cycle thereafter.

4.7.8.4 Firing procedure. Firing shall be accomplished in 50 cycles using 30 round magazines. One (1) firing cycle shall be as specified in TABLE V. Cooling of the barrel shall be to the point that it is capable of being held by the bare hand. Supplemental cooling is permissible in the hand guard area.

TABLE V. Firing cycle.

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