AD-A022 357__Evaluation of 7.62 MM Cartridges Assembled With Caliber .30 API and Incendiary Bullets...

7/28/2019 AD-A022 357__Evaluation of 7.62 MM Cartridges Assembled With Caliber .30 API and Incendiary Bullets [1975]

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JAD.. .. jFA-TH-75049

EV/LUATION OF 7.62 MM CARTRIDGES ASSEMBLEDWITh CALIBER . 30 API AND INCENDIARY BULLETS

0July 1975

Approved for public release; distribution unlimited.

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""-Munitiona Development and Engineering DirectorateRHPRODOlICCO DBYNATIONAL TECHNICALINFORMATION SERVICEU, S, DEP'ArMrNt OFCOMURCtP% 0 lP tG f l lL I,VA ZZ UU.S. ARMY ARMAMENT COMMAND

FRAN KFORD ARSENALPHILADELPHIA. PEN NSYLVANIA 19137


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UNCLASSIFIEDSECURITY CLASIrICATION or THIS PAGE (WhMn Dotl letro'd)REPORT DOCUMENTATION PA(GE 51.7D INSTRUCTnONSI,-J OR',O COMPLE'TRIG FORM

Y, I. REPORT NUMUER ,VT ACCI:SON NO. 3. .IENT* CATALOG NUMBERFA-TM-75049 T4. TITLE (end Subtflle) T.YPE OF REPORT 8 PERIOD COVERn.EVALUATION OF 7.62 MM CARTRIDGES ASSEMBLED WITH_CALIBER .30 API AND INCENDIARY BULLETS L-hnical Research ReportG. P"RFORmIIIN ORG. REPORT NUMBER

I. AUTHR(.) It CONTRACT OR GRANT NUMOEC's)VERNON E. SHISLER "IIPR FX-2826-9-462

9. PERFORMING GA.GANIZATION NAME AND ADDRESS 10. PROGRAM CLEMENT. PROJECT. TASKAAREA & WORK UNIT NUMBERSFRANKFORD ARSENAL AMCMS CODE: 4110.16.0042.6ATTN: SARFA-MDS-EPHILADELPHIAI PA 19137

II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATES.,RFA-MDS-E i uly 1975SR "- 3. HURGER OF PAGES

'14. MONITORING AGENCY NAME e ADDRESVlIdiflsnfl frot. Centrohlin Up .,oe) 15. SECURITY CLASS. (of this :sporij

: , UN.CI IF I ED [ 13,. DE'CLASSIFICATION/DOWNGRADING, ( SCHEDULENI

16. DISTRIDUTION ST.ATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISrRIOUTION STATEMENT (o the abutraetenteredin Block 20, t ditissni ti Report)

12. SUPPLFMI!NTARy NOTESThe oblect of these tests was primarily to evaluate a sample of 7.62 mmcartridges a.sembled with Caliber o30 bullets for their functional per-formance and safety, with secondary emphasis on terminal performance.

19. KEY WORDS (Continue on tosos sidelecoesae mad Identify b$ block numbeo;Cartridge 7.62 mrm API; Incendiary; Smal3 Arms Ammunition;Cartridge Caliber .30 API; Incendiary

20. SSTRACT (C on en o,, r,,. eid eIt n,c,,=v mdd oby",""o', )This report describes anevaluation of a sample of 7.62 mm cartridges that were assembled withCaliber .30 armor piercing incendiaty (API) and incendiary bullets for theU.S. Air Force (USAF).The terminal performance as well as the overall cartridge performance wasevaluated. The results ar e presented in this report. In general, th eF762 mm cartridges, assembled with Caliber .30 API and incendiary bullets,

FORM -0D1 1 N 1473 EDITION OF,, 4%13OISOLETE UNCLASSIFIED

SECURiTY CLAS1IFICATION OF THIS PAGr (Pen OData .ntotm)


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20. ABSTRACT (Continued)performed satisfactorily in the 7.62 mm minigun. However, the rifling Itwist of other 7.62 mm weapons is slower than th-t in the minigun an, aidnot provide adequate spin to stabilize the bullets. The terminal per-formance of these cartridges is similar to that of their Caliber .30equivalents.It was concluded that the 7.62 mm AP I and incendiary cartridges describedin this report are suitable for minigun use.

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UNCLASSIFIEDSICUP1TY CLASSIPiCATION OPP THIS PAGM(Obm D.Va R;tte


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TABLE OF CONTENTS

4 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 2DISCUSSION . . . . . . . . . . . . . . . . . . . . . . 2CONCLUSION . . . . . . . . . . . . . . 5RECOMMENDATION . . . . . . . . . . . . . . . . . . . . . . . . . 8APPENDIX A - Terminal Performance . . . . . . . . . . . 9APPENDIX B - Safety Statements for Cartridge, 7.62MM Incendiary

and Cartridge, 7.62MM Armor Piercing Incendiary . . . 14F, DISTRIBUTION . . . . . . . . . . . . . . . . . . ...... 16

List of TablesTable1. Summary of Ballistic Evaluation, Cartridge 7.62 mm

Assembled with Caliber..30 API and Incendiary Bullets. . . . 3

List of IllustrationsFigure1. Gyroscopic Stability Factor vs Aircraft Velocity for

Foiward Fire Cal..30 API . .................2. Gyroscopic Stability Factor vs Aircraft Velocity for

Sidewise Horizontal Fire Cal,.30 API ..... ...... 7A-1. Typical API Flash at 175 Yards . . . . . . . . ....... 9A-2. Typical API Flash at 175 Yards . . . . . . ........ 9A-3. Incendiary Flash Target at 175 Yards ............ 10A-4. Incendiary Flash at 175 Yards ................ 10A-5. Flammable Liquids Target at 600 Yards. ........... 12A-6. Results of Flammable Liquids Test at 60U Ycrds . . . .. . 13


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INTRODUCTION

In 1969 the U.S. Air Force (USjiF) had an immediate requirement tofield test 7.62 mm ammunition with armor piercing incendiary (API) andincendiary capability. Since these cart-idge types did not exist in the7.62 mm family of cartridges, but did exis2 as Caliber .30 cartridges,it was decided to "ise the Caliber .30 bullets assembled into 7.62 mmcases. Consequently, in June of 1969, Frankford Arsenal received aMilitary Interdepartmental Purchase Req'iest (MIPR) from the USAFAeronautical Systems Division (ASD) situated at Wright-P!:.terson AirForce Base. That document provided for tIze fabrication of 200,0007.62 mm cartridges assembled with Caliber .30 AP I bullets, and 20,0007.62 mm cartridges assembled with Caliber .30 incendiary bullets. Thesecartridges were to be loaded to a velocity that was as close as possib1vto the Caliber .30 cartridge velocities but still within the 7.62 mmpressure limits. The 220,000 cartridges were to be linked and packedfor minigun consumption.

Approximately four months after receipt of the Air Force MIPR,assembly of the 7.62 mm API and incendiary cartridges was completed.Several tnousand rounds of each cartridge type were expended in ballisticevaluation tests in the minigun and in other 7.62 mm weapons. Air Forcerepresentation from the Tactical, Air Command (TAC) and the ASD werepresent for a portion of the testing.

DISCUSSIONThe types of teLts performed in-house at Frankford Arsenal, and the

results obtained are summarized in Table 1. While these tests indicateda satisfactory level of cartridge performs.ice, certain defiLiencies wereencountered that warrant comment.

During accuracy testing in the 7.62 mm test barrel having I turn in12 inch twist rate, it was observed that the Caliber .30 API bullet wasnot stable; while the Caliber .30 incendiary bullet apparently was. Theinstability observed in the Caliber .30 API bullet resulted in excessivebullet yawing, erratic flight (with extreme spreads in the order of 89inches at the 300-yard accuracy target), and a subsequent (decrease indown-range effectiveness. When both the API and incendiary were fired4n a special 7.62 mm test barrel having a 1 turn in 10 inch twist rate,the extreme spreads were satisfactory as noted in Table 1. It is furthernoted that when fired in the 7.62 mm minigun bartel, which has a 1 turnin 10 inch twist rate, both the incendiary and API bullets exhibitedsatisfactory stability.

During the testing of the incendiary cartridge, two bullet burstswere encountered in the velocity testing. These bursts resulted in abright flash at the muzzle of the weapon, and a subsequent loss of thevelocity measurement since the bullet did not pass the screens. To more

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Table 1. Summary of Ballistic Evaluation, Cartridge 7,62 mmAssembled with Caliber .30 API and Incendiary Bullets

API IncendiaryAccuracy (in) at 300 YardsExtreme Vertical 6.8 9.6Extreme Horizontal 5.8 11.1Extreme Spread 7.9 13.1Velocity (ft/sec) at 78 ft+70OF 2725 2692+125 0 F 2750 2739-65OF 2642 2626Chamber Pressure (PSI)+70OF 46000 41900+1250F 47400 44700-650F 43700 41000Port Pressure (PSI) 12000 11200Waterproof (Case Mouth)50 rd samplefast leaks 7 13slow leaks 26 27Action Time (milli sec)Test 1 1.251 1.300Test 2 1.246 1.280Bullet Extraction (pounds) 131 133Function and Casualty+70OF OK OK+125OF OK OK-65OF OK OKMinigun Velocity (ft/sec)at 78 ftBurst 1 2737 2728Burst 2 2796 2734Burst 3 2747

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accurately determine the rate of occurrence of these malfunctions, aCfunction test was conduc,:ed with an M60 machine gun, firing 280 roundsat a rolling paper target. In this test, no bullet burst or any otherabnormalities occurred.A number of cartridge waterproofing failures were encountered duringthe testing. These "leakers" were expected to cause no difficulties inthe end use of these czrtridges by the Air Force, providing the ammuni-tirn wa s not stored under humid conditions for long periods of time. Theammunition was, furthermore, packed in the M548 shipping and storagecontainer which is itself waterproof and airtight.A limited investigation of the terminal performance of these cartridgeswas conducted. Th e test procedures and criteria for the Caliber .30 APIand incendiary cartridges was used to evaluate the 7.62 mm equivalents.It was determined that the 7.62 mm equivalent cartridges performed "asgood as" the Caliber .30 cartridges. Other comments on the terminal ptr--formance and some representative photographs are included in Appendix A.As stated before, the API bullet wa s not stable in the 1 turn in 12inch twist barrels, but wa s stable in the 1 in 10 inch barrel. In order t,predict under what conditions the bullet would and would not be stable, anattempt was made to determine the stability factor of the API bullet.The stability factor was computed by two independent meLhods. Thefirst, a yaw-card method, entailed firing through 20 cards placed at 1foot intervals, in the bullet's path. The resultant analysis, by themethods of Hitchcock1 and of Myers 2 , yielded estimate of 1.26 for thestability factor.In the second method, moments of inertia were measured by means of atorsion pendulum and used as inputs into a previously verified computerprogram to calculate the center of pressure and normal force coefficieitby the Van Dyke, hybrid, second-order, supersonic-flow theory. Thestability factor could then be computed by standard methods and was foundto be 1.27.Both measures applied to stationary gun, and atmospheric conditionsof 590 F, 78 percent RH an d 750 mm Hg atmospheric pressure, and twist ratoof 1 turn in 10 inches. Under these same conditions with a I turn in 12inch barrel the stability factor is 0.88. The theroetical lower limit otthe stability factor for stable flight is 1.0. When the value of stabilitvfactor is less than 1.0, the yawing motion (imparted by launch effects) ofthe projectile will no longer damp out. The yaw will tend to increase, and

1Aerodynamics of Small Arms Bullets, H.P. Hitchcock, BRL Report No . 276,8 May 1942.2Stability of Experimental Caliber .60 Bullets, Second Report on Project3/137, Frank E. Myers, Frankford Arsenal Report R-714, March 1946.

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* cause the projectile eventually to tumble. In practical applications1.1 is commonly used as the lower limit of stability factor under al loperating conditions; i.e. low temperature. This provides a modestmargin, to allow for bullet variations due to manufacturing, and also fortwist variations in gun barrels.

The stability factor is partially a function of air density. Tem-perature is one of the variables that affects aii density, and alsoaffects Mach number, whtch ia turn affects the overturning moment ofthe bullet. The stability factor is also a function of both the bulletvelocity with respect to the gun and with respect to the air. Therefore,stability will be affected by firing from a moving aircraft. A curvecan be generated showing the relation between lullet stability and air-craft velocity for firing in a given direction under a fixed sa t ofatmospheric conditions. A family of such curves can be generated fordifferent temperatures, holding the other atmospheric condition constant.This was accomplished by first generating a curve of the overturningmoment derivitive as a function of Mach number using the Van Dyke hybridflow theory.

Two families of curves were generated. The first se t of curves,labeled Figure 1 is for forwrrd horizontal firing from a moving aircraftand represents the most severe condition. The second se t of curves,labeled Figure 2 is for firing horizontally sidewise from a moving air-craft. For firing at a position between for'ard (00) and sidewise (-900),and at an elevation other than horizontal, the stability value will liebetween those given by the two curves. These curves do not apply to anyfiring directed toward the rear of the aircraft.

It can be seen from the curves that, by the criterion of 1.1 as theminimum practical stability factor, the acceptable range of firing con-ditions is quite limited fo r this bullet.Upon completion of these evaluations, a safety statement for each

c artridge was transmitted to AMSMU-Q for appropriate action in accordancewith prcedures prescribed in USAMUCOMR 700-56. Thece statements,attached as Appendix B, summarize Lhe inWormation ootzined and listcartridge performance deficiencies experienced during the testing.

CONCLUSIONS

The Caliber .30 API and inzendiary bullets, reloaded into 7.62 mmcases perform satisfactorily when fLired in the minigun under specificconditio:ts. However, the basic pyoblem of instability in the 7.62 mmweapons other than the minigun makes the AP I an unsuitable design for7.62 mn cartridge.


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RECOMMENDATIONSIt is recommended that the Caliber .30 API bullet be redesigned,if possible, so that it is adequately stable in all 7.62 mm weapon

systems, should a requirement for such a cartridge exist. It is furtherrecommended that should a need exist for a 7..62 mm incendiary cartridge,additional testing be performed on the Calioer 30 bullet to determine itssuitability in all 7.62 mm'werpons,

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APPENDIX ATerminal Performance

1. Armor Piercing Incendiary CartridgePenetration was measured at 100 ytres by firing into a 7/8 inch thicksteel armor plate. The average penetration of 20 rounds was .509 inch.Fllash was observed,.on a 10-gage mild steel plate at 175 yards. Of20 rounds fired, all flashed and completely penetrated the 10-gage mild

steel plate. Tyical flash photographs are shown in the following:

IIFigure A-1, Typical API Flash at 17 5 yards

Figure A 2, Typical APL Flash at 175 yards9


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APPENDIX A (Cont'd)2. Incendiary Cartridge

Flash of the incendiary bullet was observed at 175 yards w.&th a seriusof aluminum plates. The first plate, placed at an angle of 45'. was .020inches thick. The second, E~l-ird and fourth plates were .025 ioches, .050inches and .051 inches thick, respectively. Of 20 io- L9 flashedsatisfactorily. Photographs of the target an d a t. ic .~Shownin the following:

I.tr.r~guLL A-3. Incendiary Flash TargeL 175 Yards

t ~Figure A-4. Incend~iary Flash at 175 Yards10


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APPENDIX A (Cont'd)

3. Minlgun FiringA 100-round belt each of API, incendiary and Ball M80 was fired at a

target at 100 yards. The dispersion patterns of' he API and incendiarywere as good as that of the Ball M80.In a second firing, all rounds penetrated 3/8 inch plywood at 100yards without uursting, but flashed on the dirt hill at 600 yards. Ina third firing, both API and incendiary flashed and penetrated a 10-gage mild steel plate at 600 yards. Neither round would penetrate two10-gage mild steel plates spaced 6 inches apart at 600 yards. (Firingfrom a test barrel at 1500 yards both API and incendiary flashed on a10-gage mild steel plate, but neither would penetrate.

4. Flammable LiquidsFiring into gasoline cans at 600 yards both the API and incendiary

rounds flashed, penetrated and ignited gasoline (see Figures A-5 andA-6).


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APPENDIX A (Coat'd)

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APPMIDIX:A (Cont'd) '

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APPENDIX BSafety Statementsfor

Cartridge, 7.62MM Incendiary andCartridge, 7.62MM Armor Piercing Incendiary

1. This safety statement is issued fo r 7.62MM Incendiary and 7.6.2M ArmorPiercing Incendiary Ammunition. The 7.62M! Incendiary round consists of arecannelured Cal.30 I,,rN ullet inserted in a 7.62MM case, and the 7.62MMArmor Piercing Incendiary round consists of a recannelured Caliber 30Armor Piercing Incendiary bullet inserted in a 7.62MM case.2.. Armor Piercing Incendiary Cartridge

a. Testing consisted of firing fo r velocity, chamber pressure) andfunction and casualty across the temperature range of -650 F to +1250 F -ndfo r port pressure, accuracy, penetration, and action time at +70P F ternera-ture.

b. All tests were conducted using Mann barrels except function andcasualty which was conducted using the M60 Machine Gun and Minigun.

c. Accuracy tests over a 300 yard range in a Mann barrel having a onein ten inch twist indicated an extreme spread of 7.9 inches. These resultsdenote a satisfactory level of accuracy when fired in the Minigun whichalso has one in ten inch twist barrels. Accuracy tests were also conductedusing a one in twelve inch twist barrel with a resultant 89.0 inch extremespread. Excessive dispersion patterns will be experienced when firing inother U. S. 7.62MM weapons; all of which have one in twelve inch twistbarrels.six"d. During the function and casualty firings at the -65o F temperature,six incidents of bteech flash were reported. The occurrence of breechflashes in machine gun fire is not considered hazardous.

e. Approximately 1900 rounds of armor piercing incendiary ammuniclc,Iwere fired in all of the tests and the only significant occurrence was sixbreech flashes at -650 F during the function and casualty firings.3. Incendiary Ce'rtridge

a. Testing consisted of firing fo r velocity, chamber pressure, andfunction and casualty across the temperature range of -650 F to +1250 F andfo r port pressure, accuracy, incendiary flash and action time at +700 Ftemperature.

b. During the velocity firings, two muzzle bursts occurred, one at+70C F and one at +lI5o F. Muzzle flashes were reported during velocityand chamber pressure tests and questionable muzzle bursts were reportedduring the function and casualty test. A subsequent function and casualtyretest exhibited no muzzle bursts. A muzzle burst identifies an unsatis-faccory performance involving the disintegratiofi of a bullet as it emergesfrom the gun barrel and the occurrence of an excessively loud report. Amuzzle burst ma y be hazardous to personnel or material adjacent to and

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APPENDIX B (Cont'd).I

forwaia of the gun muzzle due to shrapnel effect of the bullet fragments.The occurrence of muzzle flashes are not unusual and are not consideredhazardous.

c. Approximately 1250 rounds of incendiary ammunition were fired in allof the tests. Significant occurrences were. five muzzle flashes, four questiona-ble muzzle bursLs and two positive muzzle bursts. There were no instabiliLyproblems encountered in firing this ammunition.4. As a result of and within the scope of all of the tests performed, theonly hazards presented when firing 7.62r4M Armor Piercing Incendiary end7.62lKM Incendiary amr~nunition are those due Lo muzzle bursts when firing incen-diary ammunition.

5, In addition to precautions to be observed due to muzzle bursts when firingthe Incendiary anmmunition, all safety procedures and standard operating proce-dures exercised in preparation and execution of firing, care and handling ofany small caliber development ammunition shal'-be obs~eryed fo r both ammunitiontypes.(j/ $

CONCURRENCE: .- '- -JOHN CUMNILNGS.Drector, Quality Assurancd,'-'QlO00

.~/C.* C. FAWOEMTDirector, ADEL, JlO00

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AD-A022 357__Evaluation of 7.62 MM Cartridges Assembled With Caliber .30 API and Incendiary Bullets...

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