Historical Document · 1964
A Ballistic Research Laboratories note of August 1964 measuring the mechanical cycle of the SPIW prototypes. The Hyper-Burst Mechanisms dive cites it for the burst rates and timing the prototypes achieved.
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N~rI052 --'01 oill ! 111111"'I!'I!I bAi ,ii 'tII1 J . i TFCHNICAl NOTF '•P. 154i AUi.uSIT 1964 KI NEMATIC EVALUATION OF THE SPECIAL PURPOSE iNDIVI DUAL WEAPON PROTOTYPES (U) Richard F. Cronin Stanley S. Lentz Wallace M. Werner I BALLISTIC RESEARCH LABORATORIES I ABERDEEN PROVING GROUND, MARYLAND OM'O -4 ' ) Best Avai~lable Copy BALLISTIC RESEARCH LABORATORIES AUGUST 19614 KINEMATIC EVALUATION OF THE SPECIAL PURPOSE INDIVIDUAL WEAPON PROTOTYPES (U) Richard F. Cronin Stanley S. Lentz Wallace M. Werner Interior Ballistics Laboratory ABERDEEN P RO V I N G B-- *-m-. G RO UN D, MA R . LAND 7, 1 T T3 1 ESEA CH C LA B ORAT OR IE S TECHNICAL NOTE NO. 1541 rfCronin/SSLentz/WMWerner/rhg/mts/mrh Aberdeen Proving Ground, Md. August 1964 KINEMATIC EVALUATION OF TBE SPECIAL PURPOSE INDIVIDTJAL WEAPON PRO(JIYPES (UNCLASSIFIED) (U) ABSTRACT The mechanics of three prototype weapons are conipared and the conformance of the weapons to the Special Purpose Individual Weapon concept discussed.; procedures and results are included. Testing TABLE OF CONTENTS S(UCIASSIFITED) page INTRODUCTION ................. SECTION I: ..... COMPARISON & COINCiJJbIONS .............................. 7 . . . .. 9 Table of Weapon Parameters ....... .......... ..................... Table of Weights of Weapons, Component, and Accessories .... .... 10 ..... 11 Table of Wei~gts of Ammunition ......... ................... 12 Table of Malfunctions ........ ......... ....................... 13 Problem Areas ............. ........................... Desirable jOeqture.s SECTION II. ............ NTTIIOlDS OF MEASURENIT & ANALYSIS ..... Measurement ............... Analysis ....... SECTION III: ...................... WEAPOi, SYSTEM ........ Aircraft Armaments, Inc. ... 16 18 .... .............................. 18 27 ...................... ... 29 . ........... .................... ... 29 ... 48 ... Springfield Armory ............ ........................ Winchester .................... ............................ SECTION IV: 14 ............. ............................ ............. .... APPENDIX ............ ......................... Components of Impulse ........... Rates )f Fire ............... ...................... .......................... Physical Inasurements ........... ...................... 64 ... 86 .... 87 ... 88 .... 89 (UNCLABsIFIED) 11MTRIUCTION In December 19i2, the Army Weapons Ccamand rent proposls from ten manufacturing companies to the Ballist'- Research Laboratories (BRL) to be evaluated for the Special Purpose Individual Weapon System (SPIN). Personnel of the Interior Ballistic Laboratory (IBL) evaluated the kinematics of the various proposed systems and recomnended that prototype weapons be manufactured by Aircraft Armaments, Incorporated, and by Winchester Arms Division of Olin Industries. It was also recommended th t further research be carried out on a proposed tnree-barreled, open chamber weapon firing three cartridges simultaneously of the Wl44 or XM110 types. Later, an eleventh proposal was also receivcd f,om Springfield Armory. AR a result of the 'Vvaluations by several different groups, tae Selection Cornmittee chosp t-'_= fý owing companies: Harrington and Ricnar to each produce ten pro on (H&R), Aircraft Armaments, Springfield Armory (SPR), Incorporateu (AAI), and Winchester (WIN), e weapons as presented in their proposals. Early in March 1964, Pree prototype weapons from each ef 6W four contractors were delivered to BRL for kinematic analysis and evaluation. An extensive series of tests 9 data for n conducted to furnish tV - selecting the prototype which would be most advantageous to develop for the SPIW system. I Inival tests of the three barreled Harrington and Richardson weapon showed that the satem was hopeless: first, because the because of its exceilve weight; second, chanism could not be made to function; and third, because the thren- projectile round produced extreme variations in velocity and excessive dispersion in the target patterns. As a result, the Harrington and Richardson system was withdrawn from the program and given no further consideration. 7 The Cal. 7. 6 2mm automatic rifle Ml14 and Cal. 0.223 automatic rifle M16 were designated as ccntrol weapons and fired in the pi:ogram to provide a comparison to the comletitive systems. The kinematic analysis of each weapon system is incl-uded In the following ordf;,: Cal. 7. 6 2mm Automatic Rifle M14 Cal. 0.223 Automatic Rifle, M16 Aircrafts Armaments, Incorporated Sprin•-field Armory Winchester Arms Division, Olin Industries. The control weapons are described in the discussiun of the methods and techniques used in testing the protnt+rpe weapons, The analyses of th? prototypes f±oln'w under seierst. nieadings. Considering that the 4-rn purpose -,f this report is to furnish guidance for selecting the best overall SPIW system, the report is arranged into three main sections. Section I includes comparative tables of average values such as weights, impulses, moments of inertia, cyclic rates, and overturning moment arms, Also included are comparative tables of malfunctions, problem areas, and a general assessment of the competitive SPIW systems. This should furnish a quick and ready reference for members of the Evaluation Committee. Section II includes a discussion of the testing meth'ds and procedures, weapon operation, and analysis of the data. Section III presents information which documt rts those values &ivel, in the tables of Section I. Section IV contains a de t ailed series of tables show- ing the variations in the parameters of those weapons evaluated by IBL. CONFIDENTIAL (CONFIDE'TIAL) F P ,~"'-~ SECTION I. COMPARISON AND CONiUSIONS (U) arc tables giiving dana for the prototype and control weapons as de-termined at IBL. CONF DENTIAL CONFIDENTIAL 0 0 toi 0~~- III4 4-40 0 \ ~ An~ r4 u I, fn0 ff -H .14+ 0, ~-1 r- -) N1N r- NI 01 CONIDETIA tH C p" o o o CONFIDENTIAL I u ) :IJ to tt 14 * tNt CNINI Sr S• • I CONFIDENTIAL CONFIDENTIAL 0 0 0' 0 0 0000 0 IN H o;* . I12 o 0 0 0 H 0 CONFIDENTIA CONFIDENTIAL "•" I J • Hn Ho -0 I -)1 \O _ -1 H -I C CC) CMH.H "2' JS o* o H 0' U' H 4 -o . P I I Iop) "N o I ,- 0E o o C FH A CONFIDENTIAL CONFIDENTIAL PROBL.4 AREAS AAi------ (1) AmmitunLion must be lubricated and the chamber must be cleaned frequently to prevent case separations. (2) Lubrication of armunition produces excessive sludging of the mechanism and magazine. (3) Either the friction should be reduced or the spring force increased in the magazine to position the round in a shorter time and prevent bolt overrides. (4) The three~rolnd spiector may fail to functlon when exposed to dust, sand, and dirt because of its ccnplexity and aludging. (M) ul-cTor *. .teds to be reinforced to prevent breakage. (6) Qua][l'y control on ammuniLion is poor and causes widespread variation in implLse and functioning of weapon. SPR ------ (1) Box magazine reqLUrss further development to obtain positive feeding. (2) Extractor lip needs to be reinforced to prevent breakage. (3) Backplate buffer system needs to be revised to eliminate cracking of operating rod-bolt carrier assembly and loes of the charging lAndle. (4) A e=jor redesign will be necessary if a low rate mechanism is required. (5) Naturm frequency of barrel and cyclic rate of the gun have a phase relationship which can Increase the amplitude of the barrel vibration to the detriment of accuracy. This will moot likely be maximum with prone-bipod firing. (6) 2lastic tr!--q i-hould be reinforced to prevent brt,. tge. I4 CONFIDENTIAL CONFIDENTIAL WIN ------ (1) Floating barrel does not give a significant decrease in the extreme spread of a three-round burst as compared to that of the locked b•erel. If the floating barrel P•fect were maximized through reC-ign, the 5J level would not be obtained, except through use of ccmpensation. (2) The floating barrel concept produces most of the malfunctions encountered with the system. (3) Mhe recoil impulse of this weapon is Lhe highest and the ruzo-le velocity is the lowest (WSL data). (k) Normally, the weapon is underpowcrcd. (5) Firing r' lac"- suffi-ient energy to fire the first round con- sistently. Sometimes even succeeding rounds fail to fire beca-. :-f thp relative motion of the barrel, receiver, and the (6) Magazine has excessive friction and lacks positive support for positioning the rounds in the feed throat. (7) Fixed ejector adds excessive friction to the bolt and influences the rate uf fire. (8) Three-round hurst control mechanism is weak and poorly designed. (9) Weapon will fire upon charging mnlrss .>,i three round burst counter wheel is indexed. (10) Muzzle attachment fails to hold the stripper securely. (11) Extractor lip requires reinforcing to prcvent breakage and the extractor spring requires redesign. (10) The caming forets and torques during unlocking of the bolt are excessive. 15 CONFIDENTIAL CONFIDENTIAL Desirable Features In reviewing the fea-tures of the three weapons, it appears that the beMtu features might be combined advantageously into a single weapon. None of the Uliee prototype vreapons are capable of .,,corporating these features without extensive redesign. The desired features are as follows: Stock, Butt Plate and Sights. Whatever the material used, the weapon should have a conventional drop stock with low sights for easy and accurate aiming. The line of tij.-st or tht center line of the bore extended shou4.d be as near to the center of the butt plate as possible ",o avoid an overturning couple which tends to raise the muzzle. This is best accomplished by having the barrel and receiver placed as low as practical in the stock with much of the mechanism placed above the barrel. The n rf' ,e Winchester weapon more nearly meets this requiremcnt. The Aircraft Pmasments wcapon contains a drop stock and low sights but the line of thrust is above the heel of the butt plate, neceu~ LaLg s largo compensating ,orce to limit muzzle rise. The Springfield version contains a straight stock with the line of thrust slightly below the heel of the butt plate, but the sights are high and aiming is avkwrd unless the butt plate rests high on the shoulder, on the extreme edge of the shoulder or on the muscles of the am . Three-Round Control and Moe of Fire Selector System. The selector and burst control should be simple, positive and rugged. It is desirable that it provide a low rate of fire for full automatic firing and autcmatic re-indexing for three. round burst control. The Springfield system most nearly meets these requirements. It has a cam method of operation of a combined three-round, full autcstic and semi-automatic control unit which is durable but do-s not contain autcuatic re-indexing w I low rate features. The Winchester control unit is inadequate. 1-he Aircraft Armants system performs all functions but is complieatsd and has relatively short endurance ampabilitLeb. Selector Switch. The selector switch provided by Airer, ft Arow-,ints is advocated since it is eaai1v set, accessible, and has good locklr abilities. The Sp•-ingifeld tst:xtor zu"Itch ie the mnst d tieult to operate and moat Inace•sible of the three switches. 16 CONFIDENTIAL CONFIDENTIAL Magazine. The box type magazine is of its 6iaplicity, ease of storage, favored over the drm magazines becase ease of carrying, ease of field loading, and lower inherent friction. Stripper Replacement. and speed. Barrel. Tt should be possible to replace strippers with ease This is best provided for by the Winchester muzzle device. The barrel should be stiffened to increase its natural frequency of vibration and decrease its amplitude thereby reducing the influence of barrel movement on accuracy. Bolt Mechanism. Some method should be devised to reduce the impact forces as the operating rod or bolt carrier cams and jerks the bolt rearward and jerks the cartridge case from the chamber. extractor and reduce t' Such a method would contribute to the life of the ,Lisibility of case separations. This might take the j:Zri ni a camming effect which breaks loose the, case and provides the bolt with an initial ve±oclty priu, •u Lhe impact bct6ccen bolt and belt earrier. method which seems simpler is A second to install a relatively heavy spring between the bolt and bolt carrier which buffers their impact and eases extraction. Such an arrangement may be installed in any bolt mechaninm assembly. Ammunition. The conventionally primed round, 144i, in advocated since the multi-piece primed cartridg- XO4l1O cannot be fired successfully without lubricaLing the case and the single piece primed cartridge M190 provides marginal functioning when fired unlubricat-,A. 17 CONFIDENTIAL (LNCLASSIFIED) 3ECTION II. MEHODS OF MEASURFEOMT AMD AIULYSIS Meas urement "Dih weapons receivci for e ,,-utionand nomparison were as follows: NU4MBE SYSTEK AAI 2, 3, & 4 HUR 3, 5, & 7 SPR 11, 15, 19, 13, 14, & 17 1, 3, & 9 jo8(56 (TRv) 030936 (COIIT, AR-15, MOD. 02) WIN 1-..4 ma6 The study was concentrated upon the functioning of +.h" mechanisms and the adequacy of their cs..",nr-nt _trcs, the effect of rate of fire and barrel flexi- "oility upon accuracy, the weights of parts and combinations of components, the moments of inertia of various configurations and the components of impWlse. The pertinent measurements were made using the following techniques: Dioplacement-Time Recording•s Mechanism. For the techniques of obtaining displaeesment-time records, BRL Report No. 610 should be consulted. Each of the weapons was mon+ed in a machine rest by clamps an shovn in Figure 1. Figure 1. (UN1 M =IE) Munt for Ralt Notion StUdY 18 Firt rubber padding was used for protection. Reflectors were placed on the stook aitd on a convenient part of the operating rod. From the displacement-time records of those reflectors taken during tfaree-round afd ten-round bursts, the bolt motion csn be infer-ed. In this study, three three-round bursts and three ten-round bursts were scheduled for each of the weapons. between roundz. The rates of fire were determined from the time Represenuative cycles were selected from the records and the operating events cf the weapon were identified by measuri±%g the location or bh• part or parts if the mechanism. Fig-ran ? shows this for the M14 and M16. The representative cycles were meascured for displacement and time. Using differentiation formalas as pre;3ented in BRL Report No. 840, velocity versus time =n1 accelprattinn v .,us tme was obtained. The results were then plotted as sbnwn in Figures 3 and 4. The estimates of the accelerations associated with the impacts in the mechanisms were low due to the nature of the ntmerical analysis. checked by graphical methods. These then were Another check on the acceleration forces present was obtained by means of the displacemcnt-time information and the calibration of the springs found in the mechanism. Further, with this information the energy of the firing pin at the time of primer contact rould be estimated. 19 0 4BACK PLATE- R~EARSEAR-, z 4-EJECTION /-/ × "RFLE,CAL 0.223. MI STARTOF HAMMER / CKING I STARTOF I-UNLOCKED Sx 0 LOCKtING OF -_________ - UNLOCKING O 2 4'0 2 S 100 MOT O STOCK RTIAN F tOIS oo 140 126 240 nao N RUAR SEOEC-,N, I ' I I I I o I 1 I , I I I ' '. . "AA . . M _____f__-,CL_.O 1 STERT Of R-. 06 START OF TPI FI•IIA PLATtECM[Tvs TM 0-- I I O0 ~ 2 AMNzr~e 40 SO 16 010 FIGURE 2 Itio 140 TME. V SIC ISO DISPLACEMENT vs. TIME 3 WOJNOVST~l 2W0 220 240 260 0 V .0 w w *u >e 0.I U- ___ _ ID~ IT N-0 10 ~ -, ----I0 0 -N IA.IW13A 21 La 0 0 0D 2.0 1 3Sa IAMVdI 'NOILW~313W z 100 00ý jf 42 Displacement-Time Recording, Muzzle. The weapons were fitted with reflectors on the muzzles such that the vertical oscillation of the muzzle could be obtained. The same weapon mounts were used as shown in Figure 1 except the forward support was moved back to the fore-grip 4. shown in Figure 5. Figure 5. (UNCLASSIFIED) Mount for Muzzle Motions Study Three thaee-round bursts and one area round were fired for each syatem. Displacement-tine records obtained provided the basis for estimating the angle of the barrel at the muzzle. estirates. Targets were measured to provide a check on these Figure 6 shows records of the barrel motion for ,he K14y, "16, M.16 outfitted with a combiuation muzzle brake and compensator (:UC). 23 and the P -02 -8. 19 -2 e ~s1 1 r12 Lo 224 h The time of projectile emergence is time record as fiducial lines. optics of the drum camera. recorded directly on the displacement- These are produced by the muzzle flash and the The fiducial lines provide a mears of determining rate of fire and the effect of' '! interaction of rate of fire and natural frequency of the barrel on target patterns. Wc ,;hts. The weights of components of the systems and of various combina- tions were determined by means of a balance scale. Moments of Inertia. The moments of inertia of each weaion were determincX.i by torsioral pendulum techniques similar to those described in BEL Technical Note No. 874. The weapons were placed on a previously balaneed tray which hung by a ,,!ire as shown in Figure 7. Figure 7. (UNCLASGIM-F) Apparatus'for Determining Momento of Inertia 25 The tray and weapon conbination regains balance when the center of graivity of thne weapun f. vertically bcnoath the wire. A stylus, colinear with the wire, was used to mark the location of the center of gravity on the weapon. The tor- sional period of oscillation about the wire of the tray and weapon combination This leads to the value of the moment of inertia about the wire of was measured. the combinations. Subtracting the moment of inertia of the tray from this value gives the moment of inertia of the weapon about an axis parallel to the wire axd througl the center of gravity of the weapon. The moment of inertia about a par- allel axis through the center of the butt plate is calculated from this value, the known weight of the weapon, and the distance of the center ')f gravity rrom the cente'. of the butt plato. Cqn•.....ta bal'i crfImpulse. Lic pendulm. Nu. 955. The measurement of impulse is achieved by use of a The tek-,-!qAuen ar. described in ML 4aaorandeum Report Each of the weapons was mounted in a three-wire perdulum, first on the side to measure recoil impulse and the component of impulse vhich is dovnard at the muzzle, and second, rotated 90 about the bore line to measure the recoil component and the leftward component of impulse at tho muzzle. The technique vw fired for each of these two conditions. Ten rounds were sumplified for thic study by placing a stngle stylus at the center of gravity of the pondul•a bob wnd recrding the motion of the bob on a horizontal surface as sbown in Figure 8. Figure (ULMASSIFM) Weapon Mounted in Three Wire Dallintic Pendulum 26 The line drawnr is parallel to the resultant impulse vector and its length is proportional to the magnitude of the vector. This test use carried out by the Dlevelopment and Proof Service. Parts Life said Impacts. Impact forces, in general, are a measure of the life of t~.e components in a weapon. The more severe the impacts sustained, the less the longevity that can be exmected for tae parts involved. The accelerations at Lm act the bre~h, sear, unlocking and at the rear bu~zfe~r can be transtfrr.-d to any desired component of the bolt to estimate the force on that particular part. To obtain the accelerations and their corresponding forces, an averfe~e round of a burst wias selected end the displacement-time reeord oi that round differentiated to obtain both -' 4. nQ aoceleration. Since the method of differentiation cannot handle discýnntinuitiee and is inaccurate for sudden cmang.. of velocity in very short intervials of time, the acceleration bas been estimated from the displacement-time curve by the tangent method. Extraction. Since it is most difficUlt to estimate the force involved in extracting the fired case, i.e., the frictional forces between the case end chamber wallsa, the strength of the extractor must necessarily be a "cut axd try" affair. At high rates of fire, the acceleration effects become much larger. Bence the extractors must be proportionally stronger as the rate increases; end the surface in contact vith the rima Is nalno proportionally increased. Feed Kechaniams. Vlagazines should have a spring etrung enough to raise a round to the feeding lips in the time allotted by the bolt. Feeding must be positive when one rouind is in the masgmine or the magazine is tull. ]Pjectors. In general, an ejector which is fixed to the receiver instead of being a moving part of the bolt is more reliable. Barrel. Whip. The vibration Of a barri-l affezte the accuracy of a weapon since the projecti.Le is la.x".. ý accordance .th the angL. of the i. .lat the inuzzle and, to a lesser extent, the lateral velocity of the barrel at the time of projecU~le emergence.* When barrels are relatively Ug~t and flexible and 1ftvv Auz compensators which prov'ide lateral imptUles to the barrel at tý* mauzle# the 27 magnitude of the oscillations can become large. In addition, when the weapon is fired automatically, the successive projectiles can emerge at times when the muzzle deviates considerably from the rest, aimed position. Further, Lim rate of fire of the weapon can be such tha 3ucceeding lateral impulses accentuate the oscillation remaining from previous rounds. The rate of fire of the weapon can be chosen to be compatible with the natural frequency of the barrel but this hrrangement will be lost if a bayonet and/or bi-pod is atta'hed to the muzzle. It also will fail la, so far as the rat; of fire deviates .eom the optimum. In gene,'al, it is better to stiffen the barrel. Whenever the weapon is fixed with respect to th,, grcud in vary!ne degrees of rigidity, the ampliL."•' of ýue vibration and the accuracy of the weapon will vm according to the rigidity. In those cases where unusual or new problems arose with a weapon system, appropriate techniques were devised and are described in the section Problem Areas. devoted to that e•anpon. CONFIDENTIAL (CONFTT)ENTIAL) SECTION III: AIRCRAFT ARMAMENTS, INC. WEAPON SYSTEMS (U) SPECIAL PURPOSE INDIVIDUAL WEAPON Description The Aircraft Armaments syste is is shown in Figure 9. The point fire weapon essentially gas operated, obtaining ito energy for operation from the set back of a piston which is incorporated in the cartridge. strikez the piston moving it In operation, the firing pin forward to actuate the primer. pressure accelerates the piston and firing pin rerwarr•-, sufficient energ, The ensuing gas unlocking the bolt 'ith to cycle the mechh.ilsm at a rate of fire fiom 2000 to 2500 shots per minute in 0ontrolled three-rouna bursts. The machani~m also contains a selector which provides semi-automatic fire, three-roun.s per trigger pull and • ;'i automatic fire. 6C0-715 slw,,t•t The rat:- of ftor for fu.L. xu''amatlic fire is reduced to .; minute (SPM) by means of a time delay mechanism. is fed into thp riflol fro,. The ammunition - aprinR loaded, plastic drum muazine holding 60 rounds located imediately ahead of the trigger guard. Figure 9. (COIFIDENTIAL) Aircraft Armimsmts SPIW System 29 CONFIDENTIAL (U) CONFIDENTIAL An area round launcher is attached to the stock beneath the barrel. The launcher holds three standard 4Omm area rounds in a tandem magazine and is operated ,.-i÷i Th- area round is fired by a trigger located beneath the launcher forward of the magazine of the point fire weapon. Rubber pads shown manulij 'ý lever in Figure 10 are placed between the stock and area launcher to reduce the recoil force. Figure 10. (CONFIDENTIAL) Lwms chcr Recoil Pads 30 CONFIDENTIAL (U) CONFIDENTIAL The bolt assembly shown in Figure 11 is composed of the bolt body containing the Pxtraotor, locking cam and the locks, the firing pin contnining the zam pin, the searing surfacez, tne buffing surface, and the assembly which mates with and Since the firing pin assembly attaches the driving spring to tt.. firing pin. ser'ies the function )f an operating rod it will be so termed. composed of two separate springs in parallel, The driving spring, also serves as the firing pin spring. A heavy spring, buffer is assembled at the rear of the receiver to remove all remaining energy from the bolt assembly and return i, to battery at a relatively nigh velocity. Figure 11. (CONFI L) Bo~lt, Firing Pin and Recoil 31 CONFIDENTIAL Wp~ings 4 CONFIDENTIAL Procedure end Results Three rifles, No. 2, 3 and 4, complete with 4Omm area round launchers were delivered for kinematic analysis and evaluation. Each of these weapons was mounted in the machine rest held at the rear by a butt support and boot backed up by the soft recoil pad on the rif..; butt as shown in Figure 1?. Displacement- tiae records of operating rod motion and barrel vibration were obtained. For barrel vibration the weapon was held as shown in Figure 13. Weapon No. 3 was also fired from the shoulder to observe vertical movement using the 8houlder-eibow stance. Figure 12. (UULA8BZ)) Mount tor Dolt NotiO Stu NIL Fivare 13. (tMULABSI ) Mount for Mkzzle Hbtion Btudy 32 CONFIDENTIAL CONFIDENTIAL I together with the rates of A resume of the firings vith the three weapons V. tire and malfunctions are given i* Table TABLE V MAYOIDM~E1IAL) FUNCTIONING0 DMT (U) Airctsft Armaments, Inc. X9110, Lot AAI-6cO-I Ammunition: calpn 11o.of R6s. 11,1ber Ir~ L~a Pate of Fire (ak Reak in. MT V Three.round bursto, machine rest 2 3 2459 .. 2314 .. 2230 .. 3 2174 2035 1816 S.. .. -. -. 2 "" 2 2 .. .. .. .. Failed to feed third round Failed to feed, 12 o'clock stub go rates taken, muzzle motion Failed to extract Failed Lu extract, broken extractor .. .. Fatlc. to feed Fatiec. to feed CMane4 to No. 3 MapUine Automatic fire, machine rest V/No. 3 m.k-eisie 10 1 gl'* 7114 697 701 688 696 LoUrate Mseanim failed on last round Failed to feed, round stuck in 10 710 703 696 10 10 713 710 701 700 690 696 5OT CONFIDNTIA magazine throat CONFIDENTIAL TAM v (Cont'd) Weapon NLber No. of Fds. Rate of Fire (&=) Av. In Burst Remarks in. rest Three-round bursts, machine 3 3 3 2434 2320 2206 2338 2239 2319 2207 2299 2174 Three-round bUrbtS, mi•wzIc motion Personnel error, semi-automatic setting 3 -- -- -- J Officu.6 demonstrations) no records Broken extractor, replaced Check on extractor, shoulder fired 1 Case separationo .. .. .. 28 4 Failures to eject Automatic fire, machine rest 10 lu 10 694 731 715 687 691 685 681 676 657 Three-round bursts, machine rest 14 3 3 3 1724 2047 1974 1709 2o12 1913 1694 1976 1851 Three-round bursti, muszle motion 2 3 .. .. .. .. "". -- .. .. rounds Failed to load enouv= Failed to eject third case Failed t'ý elect ti- I ease 3O 4 CONFIDENTIAL CONFIDENTIAL TALE V (Cont'd) of Rds Wee Wn No Number In Burst Rate of Fire Max. Av. 16M) Min. Remarks Automatic fire, machine rest 12 916 766 686 8 10 860 729 711 741 684 705 679 587 696 Low rate mechanism failed on first and last rounds giving 1566 and 1538 spim Ammunition Lot C002 fired for comparison Machine rest 2 3 741 730 719 Failure of rear sear release 4 3 3 1923 1993 1876 1946 1829 1899 3 2040 1788 1542 4 1714 1677 1608 Single crimp Double crimp, low energy on last round Double crimp, low energy on first round Set for full automatic, low rate mechanism failed Amttnitior Lot 650-14 fired for comparison Machine rest 2 4 3 3 717 2190 2247 706 2174 2243 701 2158 2238 35 CONFIDENTIAL CONFIDENTIAL A tracing of a Tnree-rowid burst showing the salient points of functioning is snown in Figure 14. The time delay mechanism which -- duces the rate in full automatic fire is a&sembled at the rear of the selector mechanism. The delay element is composed of a spring loaded inertia wheel which, when struck by the operating rod toward its maximum travel, rotates the wheel. The operating rod is caught on a rear sear and is released by the impact of a protrusion on the inertia wheel as it and releases the sc r. A tracing of a burxst in automatic fire ie returns shown in Figure 15. Fioure 16 gives displacement versus time, Lion versus time of s typical velocity versus time and accelera- U.- from a tnree-round burst. The vertical motion of the muzzle was recorded when firing from the machine rest and from the shoulder-elbow position., The motion of the muzzle was obtained when firing both point target and area target rounds. obtained are shown in Figure 17. 36 CONFIDENTIAL Tracings of the records CONFIDENTIAL -8 wigI ,!E 1- -0 MI Nli.JrdSIQ N1' NI *J114Ml3)'fldSI CONFIDENTIAL CONFIDENTIAL J -L .N1 'LNJMAJVII1 C N I -4 t,.J-- CONFIDENTIAL w z -ui In> w )IK 40 22 *Nl 601 x=90 .LN33*VlglO 39 4A.100A NOU93-i" -9 In CONFIENTIA W- CONFIDENTIAL r2 I! -8 1 :1 " I Ii - a ° L. -0 • L I -• O . I * iiON "- 0 0 0 ,43 CONR1OEN.,.I.A CONFIDENTIAL The mutjua uZ Lhie zLuule was correlated with the position of the round impacts on the target. The vertical pcsition of the rounds relative to the first round are quite similiar to the direction in which the muzzle is pointing at projectile However, due to the small angles involved and other possible factors the vertical distances of the impacts with respect to the first round are different emergence. from the d!.ztances calculated by radian measurement fion muzzle motion assuming that the muzzle ,1'.iates as a cantilever beam. The correlation of muzzle Moves-'t with target impacts is shown in Table VI. CONFIDENTIAL P44 QJ toN~ 014* 0K'ýCN h" CJ 0 tr zz 0* Fii 2.00 00 as. I10I~ 42 000 CONFIDENTIAL The impact loading between operating rod and buffer was estimated from the flmprc3ion of the buffer spring obtained from ,-hp displacement-time record and from the 3Jod-deflectioa calibr'tion curve of the buffer spring shown in Figure 18. 750 f u500-J -J 250 (UNCLASSIFIED) 0. .2 DEFLECTION, IN. .3 FIGURE 18 LOAD-DEFLECTION CURVE BUFFER $POW AIRCRAFT ARMAMENT, INC. SPIW SYSTEM 43 CONFIDENTIAL CONFIDENTIAL The estimated acceleration forces occuring at several points in the bolt 'y~le Pre given as followsAcceleration ft/sec lbs Operating rod-front sear impact 11.0 x l04 After primer ignition 22.8 x l04 Impact on buffer Force 2 780 30 -- The firing pin energy for firing a first round was computed from the weight and the final velocity measured from the displacement-time records. energy measured is 70 1 6 inch-ounces. The average firlug pin energy for other rounds of s burst is _", I d inch-ounces. during the firings uf ,is The average No misfired rounds have been observea weapon system at IBL. The acceleration forces at locking and chambering of rounds were not measured because the motion of the firing pin was recorded rather than the motion of the bolt. The force of accelerate'on at unlocking and extraction of the ftred case may be obtained from the deceleration shown in Figure 16 and by assuming that the friction between the chamber and the cartridge case is zero. produces a minimum force. be 440 lbs. This assumption The acceleration force at unlocking is estimated to The extractor is also subjected to the same acceleration at unlocking but since the friction between the cartridge case and chambcr walls is unkwvta, the force exerted on the extractor can not be estimated. Discussion In general the Aircraft Armament weapon functioned well. Discussion of the component mechanisms follows. Mode of Fire Selector Wechaniam. trigger,amfety, The selector mechanism is composed of the sears, three-round counting device, 1 selector aw.tch us shown ia P- -r.. 19. intricate. low rate s.ehanism and This involves mwny ;mall prur., some quite This mechanism can be removed and replaced as a anit. The tnree-rowid control consists of a twin cog escapement operated by tne operating rud tdilh aJlJ0wa three rounds to be fed into the chamber. After the third round is :ired the escape- ment is returned to its original position by a spring if the trigger is released. 4ID CONFIDENTIAL CONFIDENTIAL Following liree-round bursts can be fired only by releasing the trigger. Thus the e-caperpnt has the facility of being indexed for three-round burst whenever the selector switch is shifted from full automatic or semi-automatic to a three. round burst setting. kmgre 19. (COMnDITAL) The low rate mechanism is ibde or Fire Control Masc•nm i composed of an inertia wheel and clock spring. vWhen the opdrating rod is near its maximum recoil, it wheel. u) hits a projection on the The wneel rotates against the spring while the operating rod is the rear sear. held on Upon return, the inertia wheel releases the sear allowlvg the bolt tc return to battery to repeat the cycle. The rate of fire is r-duced by this time-delay methanism i', wi-over 2000 shots per minute to approxinmatuly 700 shots ppr minute. The time-delay unit does not always operate, particularly when hard extraction produces short bolt travel. delay units of other weapons, its Based on past peIrfozw.nce of the time- functioning is ltfe limited. 45 CONFIDENTIAL. expected to be erratic and its CONFIDENTIAL Feed Mechanism. The plastic drum magazine produces a slim silhouette and occupies little space for the number of rounds held. However, the magazines are difficult to load in the fiejd, have a variable spring tension and have variable time of positioning the round in the feed throat. In those instances where failures to feed have occurred it is believed that the round positioning time is Additionally, the drum less than the time allowed for positioning by the bolt. feed tnroat ig directly under the breech of the gun. A,!,of toe carbon, smoke and oil from the o.ied rounds is fed directli into the feed drum. This situat ion rreates excessive friction in the magazine and may have some effect on extraction bzcause of carbon paarticles adhering to cartridge cases. E ecto... The e ': "j rixed with respect to the receiver and should be quite positive in opcration. gun No. 3. However, ,ix failures to eject were noted with No definite opinion is formed as to the cause of the failures to eject. Several The extractors in the three weapons fired appear weak. Extractor. have been broken and replaced and several failures to extract other than caused by a broken extractor have occurred. Because of the high acceleration at case extraction hnd the configuration of the components of the bolt, the extractor must be unusually strong to endure. Chamber. The Ai-craft Armaments rifle seems to be quite succeptible to dirt Tle accumulation of dir'. causes case aocpa.:a on the walls of the powder chamber. tion, hard extraction and wtdue strain on the extractor. Beeauie of the short time from ignition of the primer to beginning of extraction, excessive amounts of powder gas residue are blown back from the bore requiring frequent cleaning of the powder chamber. Barrel Whip. The vertical vibration of the barrel during firing when held more or leba rigidly in a machine rect is considerable. stLo~ld-el'rjw ::-:.t position the at the wizzle to reduce the %,tionstill persists. When firing from the The comen(t -, placed .endency of the weapon to move upwerd when fired from the shoulder, causes the barrel to bend and vibrate under the relatively strong downward thrust of the escaping powder gas. Resume/ The Aircraft Armaments SPIW system uses a conventional drop stock with the operating mechanism high in the stock and low iight., for easy aiming. is short with a relatively short portion unsupported. CONFIDENTIAL The barre_ The muzzle compensator CONFIDENTIAL causes excessive bending and vibration of the unsupported portion of the tube when the weapon is held more or less rigidly. The weapon, because of itu primer piston operation, has a simple in-line bolt which makes it best able to withstand the high accelerations imposed by i.o high rate of fire. The weakest c•omponent of the bolt found to date is the extractor which is too lightly constructed to withstand the effects in extracting cartridge cases which at times may be difficult. The three-round control system is a relatively complicated escapement movement which may not have long endurance qualities. automatic rese to fire three-round burati- The c-ntrol system contains an whenever the selector switch is so set. The plastic drum magazine appears unable at all bult velocities to position the incoming round for feeding, either because of low spring tension or accumulation of dirt. Except for the tý Z-rouna control system and the flexible barrel the wea.porn np et.o 1ficiently rugged for military use. CONFIDENTIAL CONFIDENTIAL (CONF.) SPRINCTIEU ARMORY SPECIAL PURPOSE MIVIDUAL WEAPON (U) Description The Springfield Armory weapon is - conventional gas operated mechanism firing tn, conventionally primed XM144 cartridge. Figure 20. (COVFIDETIAL) Tne sysLem is shown in Figure 20. Springfield Armory SPIW System (U) The main portions Gf the operating mechanism are housed in the rifle stock The weapon is equipped with a selector switch enabling it to fire semi-automatically, controlled bursts of three-rounds and fully automatic. The weapon contains no rate reducing mechanism and fires both automatic fire and control'ed thr-•c. round bursts at the rate of 1>XJ - ±70) shots per minute. A muzzle-t1te-compensator is used to reduce muzzle climb and dispersion. Ammunition is fed to the gun from a sixty-round box type magazine located behind the pistol grip and trigger guard. CONFIDENTIAL CONFIDENTIAL The launcher is mounted beneatn the barrel and is attached rigidly to the barrel guard which is an integral part of the stock. The launcher is automatically operated by blow-back andr fires a 4vmm areu rou•L d fed from a + magazine. ro-nmd box Area rounds are fire' by a sepa