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/ Reproduced FromBest Available Copy,

February 1976 *

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Approved for Public Release - Distribution Unlimited

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Technical Support Directorate"41U.S. ARMY ARMAMENT COMMAND

FRAN KFORD ARSENAL

PHILADELPHIA, PENNSYLVANIA 19137

1)1 SI'S I TlON 1 N!TRUCTIONS

)'cqtroy this riepirt when It is no lonR•er needed. LI not: return it t,

the originator.

it-2ePrOdu1er FromBeSt Available COpy

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The findings In this report are not to be construed as an officialDeportment of the Army position unless 8o designated by other authcr17ed([ r•culmenrits.

IINCIASS I ] El)SECURITV CLASSIFICATION OF THIS PAGE (Wbeo. DOaf. Xnter.d)

REPORT DOCUMENTATION PAGE READ INSTRUCTIONSREPORT ......-- PAGEBEFORE COMPLETING FORMFA-"R-7tO' 2. GOVT ACCSSION NO. 3. RECIPIENT'S CATALOG NUMOI R

FIRING SHOCK MEASUREMENTS ON THE M16 R.FLE-,/M403 GRENADE I AUNCHER SYSTEMj'rest Re6oSt,

7. AUTHOR(*) 1. CONTRACT b''nANTITUOi8ER(.i7-Harvey I. Goldman

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASKAREA 6 WORK UNIT NUMSERS

Environmental Branch, SARFA-TSE-E IW662603AH78AA06

It. CONTROLLING OFFICE NAME AND ADDRESS

Fire Control Development & Engineering Dir Febe •76Frankford Arsenal, Attn: FCA-A ,--

2414. MONITORING AGENCY NAME & ADDRESS(Il dilffernt from Controlli ,•Iflce) 15. SECURITY CLASS. (ol tht. report) -

Unclassified

ISa. DECLASSIFICATION/OOWNGRADING

SCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for Public Release - Distribution Unlimited.

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/ - /- V~;..~s;)/ , .

J Ig. KEY WORDS (Continue on reverse aide it nocesoary and Identify by block number)

Mini-Laser Rangefinder! Sight Dynamic AnalysisM16AI Rifle ShockM203 Grenade Launcher" , Shock Spectrum ,

*AUSTAACT FC.1ttn. w reverse oldk. It necessary and identify by block niinaher)

A firing program carried out on an M16 Rifle with an M203 GrenadeLauncher attached is described during which shock measurements wereobtained on a mock-up of a proposed Mini-Laser Rangefinder. Firingdata obtained using 40 mm and 5.56 mm Ammunition.

DO I ̀AM? 7 1473 EotioN o0 I Nov SS IS OUSOLETE UNCLASSIFIED

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/i 76

LJNC1AS'i I F I ED)SECURIVY' CLAWISCMAYION OF ~TSI PAOII(.Yho ZWO 06#0004V

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TABLE OF CONTENTS

P.agel

INTRODUCTK)N ..................................... 3

WEAPON DESCRIPT IN ................................ 3

AMMUNITION DESCRIPTIO.N .............................. 5

DYNAMIC ANALYSIS .................................. 5

MOCK-UP OF THIE MINI-LASER BANGEFINDER .................. 6

TEST PROGRAM AND INSTRUMENTATK)I•....................... 9.

DATA PROCESINGG ................................... 11

RESULTS.................................................. 11

DISCUSSION OF RESULTS................................ 12

CONCLUSIONS ...................................... 1.14

RECOMMENDATI)NS.........................................14

APPENDIX A (SELECTED ACCELERATION-TIME HISTORIES) ........ 15

APPENDIX B (SELECTED SHOCK RESPONSE SPECTRA) ............. 19

LIST OF TABLES

Table Pg

1 Accelerometer Pvuitions ............................. 9

2 'rest Firing Conditions .............................. 11

S~1

LIST OF ILLUSThATIONS

Figure ~g

1 M16 lUIlle/M203 Grenade Launcher System ............. 1

2 Close-up of the Mock-up Wlx With Cover leinovwxl ........ 7

:3 Top Vie, w of Weapon Depicting Mock-up Mounting Technique . . 8

4 Accelerometer Mounting Locations ..................... 10

A-i Acceleration-Timc History of a Typical M203 GrenadeLaunched Gunfire Shock . .......................... 16

A-2 Acceleration-Time History of a Typical M16 lifleGunfire Shock (Semi-AutDnmatic) ........................ 17

4.'-

A-3 Acceleration-Time History of a Typical M16 IHifleGunfire Shock (Automatic Burst) ......................... 18

B-1 Siock Spectrum of a Typical Grenade Launched GunfireShock- Transverse Axis . ......................... 20

B-2 Shock Spectrum of a Typical Grenade Launched GunfireShock-Vertical Axis ............................. 21

B-3 Shock Spectrum of a Typical Grenade Launched GunfireShock- Longitudinal Axis .......................... 22

B-4 Shock Spectrum of a Typical Rifle Gunfire Shock-Transverse Axis ............................... 2.

B-5 Shock Spectrum of a Typical Rifle Gunfire Shock-Transverse Axis ............................... 24

B-6 Shock Spectrum of a Typical Rifle Gunfire Shock-Longitudinal Axis ............................... 25

2

$1 tINTRODU CTI(ON

The Frankford Arsenal has been engaged in the development of fire controlinstruments for most of the Army's weapon systems. These instruments range

from complete integrated systems for major vehicles to small arms sightingdevices. One of the major accomplishments has been the development of lacr

rangefinders which pinpoint target distances. In the past this type of fire con-

trol has been used almost exclusively in large weapon systems such as tanks,howitzers and even aircraft, such as helicopters. Consideration is now beinggiven to adapting a minilaser rangefinder to a small arms system. Probablythe most severe environment this fire control will be subjected to is the high

intensity shock resulting from firing of the weapon. TIhe instrument must notonly structurally survive the firing shock but It must also maintain boresightwithin extremely close tolerances.

This report describes a data measurement program which was undertaken

in order to gain information on the firing shock environment of a small armsfire control system. In these tests shock measuremrents were obtained on an

M'6 rifle with an M203 grenade launcher attached. While the program wasprimarily concerned with describing the shock environment at the mountingpoint of the range finder, the data obtained should also provide a useful guidein the design and testing of other M16 rifle mounted equipment.

WEAPON DESCRIPTION

]'he weapon used in this test program is shown in Figure 1. It consistsoY twr, systems, the M16 rifle and the M203 grenade launcher.

Tte M16 rifle is a 5.56mm, magazine-fed, gias operattd, air cooled,shoulder fire weapon. It has semi-automatic a -d full automatic firing capa-

bility. The M203 grenade launcher Incorporates a 40mm ammunition systemwith the MI6AI rifle. The launcher is a breech loaded, single shot, rifledweapon. The bariel slides forward on a dovetailed rail for loading or ejecting.The M203 is mounted directly below the barrel of the rifle and It has a separatetrigger.

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NM MUNITION DL1)I'S RIPTION

The M16 fires a 5.56mm caliber round which has a total weight of 179grains. The bullet head (projectile) alone weighs 55 grains. Standard bal!propellant is used in this test. The M203 fires a 40nam caliber round whichnas a total weight of approximately 0.5 l1. (0. 2 3k,). Ani XM387E4 proofcartridge is used in this program. This cartridge is produced for use duringweapon acceptance tests and contains no warhead or explosive.

DYNAMIC ANALYSLS

A simplified dynamic analysis of the weapon was made prior to the fieldtest. This was done in order to gain some insight for estimating the maximumnaccelerations t•l be measured when the gun would be fired. A Imowledge of the

maximurn accelerations is useful both for Initial calibration of the instrumentationand also for checking the validity of the measured data.

From reference 1, the maw:lmum accelerating for-ce to the weapon from the

firing of 5.56mm ammunition is estimated to be about 2090 lb. For a loadedtest weapon which weighs about 11.5 lbs, the maximum acceleration impartedIn the direction of the shock Is given by

2090Weapon Acceleration = - 180 g's

11.5

The maximum accelerating force to the weapon from the firing of the 40namammunition is estimated from the peak of the pressure-time history. Perconversation with Mr. Rabert Smith of Picatinny Arsenal, the maximumtheoretical chamber pressure for the grenade ammunition Is approximately

1 Firing Shock Measurements on the M16 Rifle, Memorandum Report M72-5-1,

by James H. Wiland, Frankford Arsenal, Phila., Pa. April 1,972

5

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3000 lbs per square inch. For t diamtcr of 40mm (. 7H7 in. radius) Lhemaximum accelerating forec is given by

2 2F = wr p w (.787) (3000) :-5840 lb.

The corresponding acceleration to the weapon which weighs about 12 lbswhen loaded is found as follows:

Weapon Acceleration .. .= 487 g's12

Therefore, the expected peak accelec.ation In the longitudinal axis duringgrenade firing should be approximately 487 g's. The corresponding pulsewidlh should be less than a millisecond.

MOCK-UP OF THE MINI LASER RANGEFINDER

Since there were no prototypes of the laser rangefinder available for thefield test, a mock-up box (weight = 1 lb, dimensions = 4" x 3" x 2") was made.The design conslderat,,ns on the weight distribution necessitated the weldingof a small aluminum blonk inside of the box onto the face mounted to theweatpon. The mock-up is bown in Figures 2 and 3.

A reflex collimator sight mourt w1s used to fasten the mock-up to therifle. Although not intended for usi with the laser rangefinder, It was theonly mount available which would fixture the dummy sight In the approximateusage position. In order to permit fastening of the mount, it was necessary tomachine off the front sight post and most of the rifle carrying hmdlle. Sectionsof this handle were machined into two webs, one forward and one rearward.The mount straddled these webs and was secured by both torqued machinescrews and pins. The mount, itself, consisted of three basic components;a baseplate which was fastened to the weapon, an elevation adjustment barhinged on the forward end of the base plate, and an azimuth adjustment barhinged vertically on the elevation adjustment bar. All adjustments were lockedwith jam screws and setscrews.

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Fpigre 3. Top Viewt Of WeaPon IDePicting Mock-Up Mounting Technique

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TFST P (IRAINi AND INST IU NIENTAr( )N

The firings and datu acquisition were made at, the Frankford Aroenal testranges located at Fort Dix, New Jersey, on 23 July 1975. The F. A. Mobilehnatruim ntation Laboratory was driven to the test site, and used for signalconditioning and tape recording tUe data. The test instrumentation consistedof the following:

1. Three piezoelectric shock accelerometers, Endeveo model 2225.

2. Three "zero drive" signal conditioning systems, MB model N400amplifiers and line drivers.

3. One 14-channel Sangamo model 3562 FM tape recorder operated at30 ips.

The accelerometers were bonded to the alutminum block Inside the mock-upusing Grip oommercial dental cement. They were oriented so that measure-ments along three mutually perpendicular axes could be obtained. The position-ing is described in Table 1 and shown in Figure 4.

Table 1. Accelerometer Positions

Tape Channel Ace. Serial No. Direction

1 HB79 Transverne (left .- right)

2 HB31 Vertical (relative to thebarrel axis)

3 CH07 Longitudinal (barrel axis)

Firing shock data was desired for various combinationm of gun elevation,gun positioning, rifle firing rate and type of ammunition. A listing of thetest firing oonditions is presented in Table 2.

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Tablo 2. Test Firing Conditions

Ammunition Description // Pounds

1. 40mm Shoulder fire, high elevation 3

2. " ," mz•i elevation 3

3. IV ,' low elevation

4. " flip fire, high elevation :1

5. it " , med elevation 3

6. " " low elevation 3

7. ' Arm pit fire, high elevation

8. " " " " ined elevation 3

9. " " " " low elevation :3

10. 5.56mm Low, semi-auto 5

11 " Bapid, semi-auto 5

12. " Burst, automatic 10

13. " Burst, automatic 7

During the grenade firing, high elevation was approximately 45°. Medium andlow elevations were about 300 and 150 respectively.

DATA PlOCiSSING

The data was returned to Frankford Arsenal where it was processed fordata analysis. Oscillograms and shock spectra were made for each teat condi-tion. The oscillograms contain information in the form of acceleration-timehislories and are used to describe the shock in termrn of peak G-level, pulsewidth and pulse shape. Shock spectra, which are plots of acceleration vs.frequency, can be used to evaluate the damage potential of the shock environ-ment. Each frequency represents the natural frequency of a single degree offreedom system and the accelerations are the maximum accelerations eachsingle degree of freedom would experience when subjected to the given shock.For the example of the mock-up of the laser rangeflnder, a shook spectrumobtained near the mount can be used to determine the input acceleration to the

11

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fire control if it were considerml tas a one (.cgrce of freedom system and sub-jocted to the gtui-.ire shock.

R ESI. LTUS

A sampling of oscillograph records are prosented in figures A-i, A-2, and

A-3 axv selected shock sprectra are Pbown in figures B-1 thru B-6.

DLNCUSSION OF RESULTS,

After reviewing aL, the time histories ayxl shock spectra for the grenadefiring, it was apparent that the shock was independent of the gun oriertation.The results of high elevation firhig were identical to medium or low elevationfiring. There was also ixo significant difference between records when theweapon was supported against the shoulder and records with the weapon sup-ported under the gunrar's arm pit or against the hip. 'Therefore, the oscillo-grams and shock spectra shown in this report represent the typical grenadelaunched gunfire environment for the M203 system.

Examining the time history response for the grenade launched gunfire con-dition (Figure A-i), the longitudinal axis shows an initial high frequency shockof about 480 g's and C. 5 ms. 'This is followed by a short duration of highfrequency and a damped vibration with a period of about 11 ms. [be initialpeak is representative of the mock-up response to the shock from the com-bustion pressure-time history. The short duration of high frequency isprobably due to the response of the aluminum block welded inside the mock-upvibrating at its resonance. The damped vibration, when taking into considera-tion the result along the trarisverse axis, is indicative of the mock-up behavingas a torsional mass-spring system with a natural frequency of about 90 Hz.The oscillogram along the vertical (relative to the barrel) axis indicates thatthe mock-up is much stiffer in this direction and the measured acceleration-time history is the high frequency response of the aluminum block. The os-cillogram in the transverse axis shows the 90 Hz. damped residual vibration.Two axes, longitudinal and transverse, both shuwing residual motion at anidentical frequency indicated a rotational (torsionel mode) vibration nbout thevertical axis.

The shook spectra (figures B-i, B-2 and B-3) clearly lhow the largeresponses at about 90 Hz. in the longitudinal and transverse axes. A signifi-cant result In comparing the three shock spectra is that the curve from the Ion-gitudLual exim is the highest throughout most of the frequency range. This in-dicates that most severe damage potential is in this axis. (In stating "most

12

never( damage potential", the failure mode is considered to be bending). Therelatively largo rosponses in all three srvctra in the region from 3000 to 400011z. are not oonsidolrod as criticpl as the lower frequency rerponscs. Th,mount for the mini-laser range finder, which has yet to be determined, willprobably have a resonance well below a fe.w thousand hertz and hence, it willprovide Atructural filtering which will attenuate the high frequency componentsof the gunfire shock.

A comparison of the longitudinal shock spectrum to theoretical spectra ofsimple shock pulses reveals that a 400 g, 0.5 ms half-sine pulse would pro-duce about the same effect on the weapon as the gumfire shock. Using a simi-lar procedure, the effect of the transverae and tertical shocks could beapproximated by 100 g's, 1. 0 ms. and 250 g's, 0. 5 me. half-sine pulses,respectively.

Examining the acceleration-time history from the firing of 5,58mmammunition (figure A-2), the largest shock, as expected, occurs in the longi-tudinal axis. This shock has a peak of about 250 g's and is 1. 0 ms. in daration.The responses in the other two axes are much lower. The rifle gunfire shockis seen to contain a second large transient about 70 me. after the initial shock.In considering the mechanics of the rifle, this phenomena is attributable to thebolt going into battery. In the vertical ai;.! transverse axes, this shock isgreater than the one produced by ammunition igpition. In looking at the recordof burst tiring (figure A-3) it is seen that this shock does rot occur after thelast round in a group has been fired. This • because the bolt is preventedfrom going into battery if no round is presen..

In comparing the shock spectra of the rifle firing to those spectra fromgrenade firing, it is apparent that the grenade produces a higher level shock.The 96 Hz. resonance response is much less pronounced in the rifle gunfireshock and yet there is not much difference between the spectra in the highfrequency range (greater than 2000 Hz). In comparing the rifle firing shockspectra to spectra of simple pulses, the effect on the weapon' in the longitudinalaxis can be approximated by a 250 g, 1. 0 ma. half-sine pulse. Similarly, theeffect on the weapon in the transverse and vertical axes are approximated by100 g's, 1. 0 ma. and 10" g's, 0. 5 ms. half-sine pulses, respectively.

CONCLUSIONS

1. 'he shock produced from firing the 40mm grenade is of greater Inter itythan the shock from the 5.56mm bullet.

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2. Tho niaximum sliock produced from grenade firing is about 480 g's, 0. 5 ins.in the longitudinal axis.

3. Due to the mock-up mounting technique, there is a 90 Hz. torsionalresonance about the vertical axis.

4. 'l[he shock produced from 5. 56n'm firing is of lower intensity than what wasfound in previous measurements with the MIG rifle. This is a result of theadded weight on the rifle due to the attachment of the M203 system. An in-crease in weight results in a lower accelerating force to the weapon.

5. The dynamic analysis of the weapon resulted in an expected g-level whichwas very close to the measured g-level. Hence, this technique can and shouldbe used prior to field testing.

RECO MMENMDAT]IS

7 1. Consideration should be given for the design of a special mount to be usedwith the laser rangefinder. The tested configuration, using a reflex collimatorsight mount appears to be unacceptable because of the relatively low frequencyresonance response to the high intensity shock produced by the grenade.

2. naaed on shock spectrum analysis, the following laboratory shock pulselevels can be used to approximate the effect of the grenade firtag on theweapon:

Longitudinal Axis - 400 g'a, 0.5 mes., half sine

Transverse Axis - 100 g's, 1.0 me., half sine

Vertil Axis .- 250 g's, 0.5 ms., half sine

14

A PPENDIX A

Selected acceleration-time lIistorias of M16 Rifle With M203. Grenade LauncherAttached.

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APPENDIX B

Selected Shock Response Spectra For M16 Rifle With M203 Grenade LaumcherAttached.

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DISTRIBUTION

Commander Commander

Rodman Laboratories US Army Infantry Board

Rock Island Arsenal Fort Benning, GA 31905

Rock Island, IL 61201.1 Attn: ATZB-IB-PO,

4 Attn: SARRI-LS-I, Capt. Mederioe

Mr. G. CookseyCommander

Commander Frankford Arsenal

US Army Armament Comumar.d Philadelphia, PA 19137

Rock Island, IL 612011 Attn: SARFA-FC

4 Attn: DRSAR--RDT,Mr. W. Romans 1 Attn: SARFA-FCA (Proj File)

3 Attn: DRSAR-RDG-S, 10 Attn: SARFA-FCA-A,Mr. J. Ackley Mr. Casper

Commander .3 Attn: SARFA-TSP-L/51-2

Picatinny ArsenalDover, NJ 07801 1 Attn: SARFA-TD

3 Attn: SARPA-AD-D-W, 5 Attn: SARFA-TSE-E,Mr. R. Smith Mr. Goldman

Comiander I Attn: SARFA-TSEUS Army Electronics CommandFort Monmouth, NJ 07703 1 Attn: SARFA-TS

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Commander 1 Attn: Commander's Reading FileAberdeen Proving Ground, MD 21005Attn: STEAP-MT-M, 2 Actn: SARFA-QAF-RMr. J. Feroli

DirectorShock Vibration Information CenterCode 8404,Washington, DC 20375

CommanderUS Army Infantry Center (USAIC)Fort Benning, GA 31905

4 Attn: ATZB-CD-MS-F.Capt. R. Dean

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