,- TRIGGER PULL TESTING M16A2 RIFLE M4 CARBINE

1 ,- TRIGGER pull TESTING_. M16A2 RIFLE & M4 CARBINEFINAL REPORTM16 RIFLE TEAMD TC0 C1 26 1993 .' ". ,.:.-.:c ,, , ppgovedfor pubhi -,nd Sale; itsdistribu:ioan IC uniimitedPREPARED BY:JOHN KREIDERAUGUST 199393-25361I~l~llilLllll~llilliilll! ; ,, 31 0 2 0 uREPORT DOCUMENTATION PAGE READ INSTRUCTIONSBEFORE COMPLETING FORM1. REPORT NUMBER 2. GOVT ACCESSION NO. 3, RECiPIENT'S CATALOG NUMBERSMCAR-ES-93-14. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVEREDF inal ReportTrigger pull TESTING , M16A2 RIFLE & M4 CARBINE May 93 -Aug 936. PERFORMING ORG. REPORT NUMBERSMCAR-ES-93-17.

2 AUTHOR (S) 8. CONTRACT OR GRANT NUMBER (S)John D. Kreider9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK AREA &WORK UNIT NUMBERSARDECSMCAR-ESW-S, Rock Island, IL 6129911. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATEAug 9313. NUMBER OF PAGES3914. MONITORING AGENCY NAME & ADDRESS (if different from Controlling Office) 15. SECURITY CLASS (of this report)Unclassified15a. DECLASSIFICATION/DOWNGRADINGSCHEDULE16. DISTRIBUTION STATEMENT (of this Report)Distribution is unlimited kk -'ntC-,',* --0_v17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report)18.

3 SUPPLEMENTARY NOTES19. KEY WORDS (Continue on reverse side If necessary and identify by block number) TRIGGER PullM16A2 RifleM4 Carbine20. ABSTRACT (Continue on reverse side if necessary and identify ny block number)Using the current procedures of MIL-R-63997 for M16A2 Rifles, 22% of random TRIGGER pulls taken failedthe requirement of pounds. Based upon an acceptable failure rate of 1%, TRIGGER pull shall betaken three consecutive times with a requirement of to the current procedures of MIL-C-70599 for M4 Carbines, 65% of random TRIGGER pulls taken failedthe requirement of pounds.

4 Based upon a acceptable failure rate of 1%, TRIGGER pull shall betaken three consecutive times with a requirement of 5 20n73 1473 FINAL REPORT: TRIGGER pull TESTINGM16A2 RIFLE & M4 CARBINEAUGUST 1993 BYTJOHN D. KRE DERG eneral EngineerTECHNICAL REPORT NUMBER: SMCAR-ES-93--1 Approved KOTECKIC hief, Sm Cal Wpns Sys DivDisclaimer: The findings of this report are not to be construed as an official Departmentof the Army position unless so designated by other authorized pull TESTING - M16A2 RIFLE AND M4 CARBINEFINAL Introduction: During May 1993, SMCAR-CCL-LP and SMCAR-ESW-S performedtrigger pull TESTING at Picatinny Arsenal to determine the TRIGGER pullcharacteristics of the latest production M16A2 Rifles and M4 carbines.

5 Theentire TRIGGER pull test consisted of five subtests plus an additional subtestusing TRIGGER mechanisms from Anniston Army Background: The TRIGGER mechanisms for both the M16A2 RIFLE and M4 CARBINE operate in the sama manner. When the weapons are in the "SEMI" modethe TRIGGER pull value is dependant upon the friction between the hammer andtrigger, and the loads applied by the hammer spring, TRIGGER spring, anddisconnect springs. when the nose of the burst disconnect is in a deep notchof the burst cam, the disconnect spring is partially compressed. When thenose of the burst disconnect is in a shallow notch of the burst cam thedisconnect spring is further compressed, resulting in a higher TRIGGER pullvalue.

6 Therefore, TRIGGER pull values are less when the nose of the burstdisconnect rests in a deep notch of the burst cam as opposed to a shallownotch of the burst cam. (See Figure I)The Depot Maintenance work Requirement (DMWR) requires that TRIGGER pulltesting be performed three consecutive times to ensure the TRIGGER pull shallbe taken for one deep notch and two shallow notches. MIL-R-63997 andMIL-C-70599 let the contractor decide how many times the TRIGGER pull shall betaken. This difference in TRIGGER pull acceptance methodology has resulted ina large number of failures using the DMWR method, and minimal failures usingthe MIL-Spec Description of Equipment:a.

7 25 M16A2 Rifles from contractor A. Rifles were obtained from thelatest production of contract 25 M16A2 Rifles from Contractor B. Rifles were obtained fromthe latest production of contract DAAA09-88-G-0004 30 M4 CARBINE burst disconnect springs from Contractor TRIGGER pull fixture from CSTA, Ft. Dix, Force gage attached to the CSTA TRIGGER pull Accu Force Digital Force Gage supplied by 20 M16A2 RIFLE TRIGGER mechanisms from Anniston Army Depot (ANAD).These TRIGGER mechanisms were from rifles that had failed TRIGGER pull ,BURST-HAMMER8UR5T CAM1 DISCONNECT, SEMIJ.

8 ,Figrure i4 f*~ Sub Test # Objective: The objective of this subtest was to determine thefollowing:a. The percent failures of M16A2 Rifles using the TRIGGER pullrequirements and procedures of MIL-R-63997, TRIGGER pull is taken in arandom Determine TRIGGER pull values for both deep and shallow notches of theburst cam for both contractors If M16A2 Rifles do not meet the current TRIGGER pull requirements inboth notches, then establish a range of TRIGGER pull values that currentrifles are capable of meeting. A 1% failure rate will be used to limit therange of TRIGGER pull values.

9 A 1% failure rate is considered as theacceptable rate of Procedure: TRIGGER pull TESTING was performed on M16A2 Rifles from bothContractor A and B with no alteration to the rifles. All M16A2 rifles weretested with the selector set in the "SEMI" mode. Rifles were lubricated andplaced horizontally in the CSTA TRIGGER pull fixture. A gradually appliedload was exerted on the center of the TRIGGER parallel to the axis of thebarrel bore. The TRIGGER was pulled 12 times (4 pulls in the deep notch, 8pulls in the shallow notch) on each of 44 rifles (22 Contractor A, 22 Contractor B) and the TRIGGER was pulled 120 times (40 pulls in the deepnotch, 80 pulls in the shallow notch) on each of the remaining six Results: Results for subtest #1 can be found in Appendix Analysis:a.

10 Analysis of Contractor A M16A2 Rifles:1. 1% of the TRIGGER pulls failed the current requirement of pounds in the deep 52% of the TRIGGER pulls failed the current requirement of pounds in the shallow 35% of all TRIGGER pulls combined failed the current requirementof Average TRIGGER pull in the deep notch is Average TRIGGER pull in the shallow notch is Analysis of Contractor B M16A2 Rifles:1. 0% of the TRIGGER pulls failed the current requirement of pounds in the deep 14% of the TRIGGER pulls failed the current requirement of pounds in the shallow 10% of all TRIGGER pulls combined failed the current requirementof Average TRIGGER pull in the deep notch is Average TRIGGER pull in the shallow notch is 22% of all TRIGGER pulls, for both contractors combined, failed thecurrent requirement of For both deep and shallow notch settings.