Historical Document · 1963
Harrington & Richardson's Phase I report of 17 May 1963 on its Special Purpose Individual Weapon design. The Hyper-Burst Mechanisms dive cites it for the H&R SPIW and its burst mechanism.
2L ;:;c". IL T I SSPECIAL PURPOSE- INDIV/IDUAL WEAPON/ MAY 11 Ma _____________ CONTRACT f INC. H[ARRINGTON & RICHARDSON, UI :DA:-11-199-AMC-27 _(W)) 1978 i•) 7A2 DOWI D AT F• YýA A Al RVAL3 DISTRIBUJTION STA'ITMENT A Ap ..-. ibhmiorn Unlimrited No. i47CO2 24 Copy ;T of 31 Best Avai~lable Copy I r4 ,1 -1- 1. INTRODUCTIti The Harrington & Richardson, Inc., S.P.I.W. concept is -based upon firing a salvo of three projectilps simultaneously out of a single plastic cartridge case containing a single primer and propellant charge. The three projectiles are fired through three individual light barrels, contained in a cluster within a single surrounding thin walled tube. The ability to index the three projectiles, accurately opposite the barrels, is due to the triangular shape of the cArtridge or "Tround" (triangular round) which is-self indexing, that is, the user aims once, fires once and three projectiles are on the way. This gives a much higher hit probability than a three (3) shot burst, as the three projectiles form essentially a circular pattern with a 3 to 5 mil spread. The use of the triangular plastic cartridge is based upon the Open Chamber Principle that has been developed over a period It may be seen that it eliminates most of the of several years. mechanism and malfunctions common to reciprocating bolt systems because no longitudinal chambering or extraction is required. 2. POINT FIRE WEAPON (SEE PLATE 1) The principle portions of this weapon are the frame or receiver, the cylinder and the triple bore barrel. The weapon uses a proposed factory loaded disposable plastic magazine containing a minimum of 25 trip~s projectile trounds or 75 projectiles. The ammunition is belted together by means of a double heat sealed tape giving a very ptrong belt which occupies a negligible amount of space. Due to the abrence of a feed spring, the magazine has an ex:tremely long shelf life. The weapon is loaded and prepared for firing by simply latching the magazine in place below the gun cylinder. A feed pawl, positioned under the topmost tround places it into the lower cylinder recess. With the safety off, the weapon may be Pulling the fired by simply pulling the trigger after charging. charging handle, rotates the cylinder 1200 and positions the first tround opposite the barrel cluster. This action also cocks the firing pin. From this point, after firing the gas mechanism performs all further functioning cf the weapon. "That is,. the cylinder is rotated 1260 ejecting the spent case and feeding the new one. This also cocks the firing mechanism. - - -Psi 1 * .I I 4- a A it ,! 11 JI -2- I:• * a If the weapon is set for "Semi-Automatic" each pall of the trigger accomplishes one discharge firing a salvo of three projectiles. With "Automatic" setting, the weapon continues to fire at. a rate of 300 to 500 rounds per minute as long as the trigger is held back. This discharges 900 to 1500 projectiles per minute. Unlatching the magazine, permits the entire ammunition belt is released, so as to enable to be rotation. as the cylinder reversewithdrawn, 3. 3PECIAL FEATURES (a) Con__tinuous Belt Feed plastic taped "Tround" permits the weapon to be used SThe effectively in assault fire by withdrawing the ammunition from a This is due to the fact magazine pouch as shown on plate #2. that the absence of a reciprocating bolt mechanism permits a very positive feed accomplished by the rotation of the Open Chamber Cylinder. (b) ProLonged Firing ¶ i Experience with other Open Chamber weapons has shown that there is far less heat transferred to the Cylinder than with This is due to'the fact that the other closed chamber weapons. insulating qualities of the plastic case prevent heat transfe; Another reason lies in the fact to the chamber wall sections. in the cylinder inherently maintained Open Chamber that the eliminates heat st6rage, Hence, it may be possible to sustain longer automatic'bursts than with other weapons. Further studies will be continued on this point. (c) Pointing Characteristics Plate #3 illustrates the relatively clean, straight top portion of the weapon. Conferences.with the Human Factors Engineering Laboratory at Aberdeen Proving Grounds, and with representatives of the Infantry Combat Development Board at Fort Benning, indicated the desirability of having a flat sight base for quick, natural pointing and.aiming against targets of opportunity. This is possible to achieve in this salvo weapon due to the fact that it is no longer important to have a straight in-line stock which is necessary with other weapons in controlled burst fire to mah1ize dispersion of the three (3) shots. i I I I I I 1 _ AIx. co U-,. - - - -- - I fri 'I 44 I I 1 '4 i - V 1 'V ) _ 5, 4. AREA FIR~E WEAPON JPLAT9S, _4, 5.& 6) This weapon is actuated by th. same trigger as the point fire weapon. A selector switch located above the trigger permits either one of the other weapon to be fired, making it impossible to fire both at the same time. A trigger safety locks the trigger in either case. A second grenade launcher safety locks out the entire breech mechanism until it Is ready for use. The launcher itself is very simple and consists essentially of a rectangular aluminum frame and a barrel. The ammunition is contained in linked plastic adapters that are fed laterally by means of a negator spring.' The trigger functions the firing pin. Upon being released, it unlatches a detent that permits the next round to be fed. Testing at H&R, Inc. shows that this design gives complete obturation within the plastic adapter, and permits accurate firing from the shoulder at all ranges up to the maximum. It is oberved that the slight lateral hift of the center of gravity of the ammunition has no effect on the lateral shift of the center "of impact even at ranges up to the'maximum. The flexibility of the linked plastic adapters permits versatility of use whereby a single round may be loaded under conditions where minimum bulk is necessary. Also, 6 or more rounds may be fired continuously from a bipod, or by supporting the ammunition by hand. Minimum loading time is required zs there is no breech mechanism to actuate. From one to. thee or more linked adapters may be loaded instantly by insersion laterally. This is the only function necessary to prepare the weapon for firing, outside of removing the safeties. The top rifle sight is used for launcher ranges up to a1hout 75 meters. Beyond that, a swiveling type of sight is withdfawn sidewkays. It permits the launcher to be fired from the shoulder at all ranges, keeping the proper sight eye relationship. (see plate #7) WEAPON CHARACTERISTICS WEIGHTS: Rifle empty, magazine in place 25 Troundi (75 projectiles) Rifle loaded Launcher empty 40 u/n Round & Adapter - S.P.I.W. empty -7.65 - 6.15 lbs. .80 6.95 " 1.50 " .53 " each lb. -4- S.P.I.W. loaded (75 projectiles & 3 grenades) Bore travel Overall Length (Without 2" stopk extension) Type of Rifle Fire - (a) (b) 10.05 !bs. 20 In. 38 In. Semi-Auto, Salvo of 3 projectiles each. Full Auto. rate 300-500 rds./min. 900-1500 projectiles/min. Muzzle velocity of .217 Sabot-Flechette ammunition -4700-4900 ft ./sec. Salvo Dispersion - 3-5 mils extreme spread. NOTE: The use of a smaller diameter sabotless projectile would permit a minimum weight saving of 1.25 lbs. on the cylinder and receiver of the rifle and wot-d permit more ammunition to be That is, the empty S.P.I.W. would stored in the same magazine. then weigh 6.40 lbs. complete with grenade launcher. 5. ACTIVITIES IN PHASE I (a) Point Fire Weapon Following the users' conference aV AWC on 28 Wepruary 1963, H&R, Inc. proceeded to build a mock-up as quickly as possible consistant with the proposed mechanism design.. In this mock-up, the grenade launcher was relocated from the top rear position as shown in the origital H&R, Inc. proposal, to 1he forward lower position. This mock-up was discussed with the Hunan Factors Engineering Laboratory on 24 March, and with representatives of the Infantry Combat Development Board a 'Fort Benning on 25 The comments of both facilities were generally in March, 1963. agreement, after independent evaluation. Accordingly, this contractor redesigned the entire configuration making several, drastic changes. All these changes are incorporated ii the present mock-up, as far as possible. Among the major changes are: 1. 2. 3. 4. 5. Location of rifle magazine forward o grip. • Flat top base for targets of oprokunity. Alter charging method for rifle.. Substitute shotgun typbrrip.for.pistol grip. Provide single trigger for both area .fire and point fire weapon with no possibility of firig •both at-owe. aolc-up .;d conrtruction While the mechanism design studies were taking place, ballistic tests wert beixg carried On independently. -CONFIDENTIALA J (-I I 2 .1 A I it coP I 1 I :71I I I I '4 L -i I I I I I I I U 0 II I I LI Il I1 I I £ 3 'I "I ii I! I 3' II 3 In March, an available triple bore fixture, using a somewhat shorter Tround, was fired to delineate the general characteristics and parameters of the proposed S.P.I.W. Salvo Tround (see plate #8). A sufficient number of Trounds were machined out of linear polyethylene (A70 Celanese Fo;tiflex) to use in the early firing tests. These tests proved out the front and rear obturation characteristics, 4 Starting in April, firing tests began with the molded S.P.I.W. Cartridge Cases and with the firing fixture made for Tests were conducted with various this program (see plate #9). propellants in order to obtain proper igAition and burning characteristics. It was found that Hercules 2400 powder (double base) produced clean burning with loads over 50 grains. Piezoelectric gage pressure measurements showed that a load of 57 grains of 2400 produced a.peak pressure of 70,000 lbs./sq. in. No sign of any case damage was shown at this pressure. In order to test the ultimate strength of the plastic case, 617.5 grains of 2400 powder was loaded (maximum capacity). This produced slight extrusion of the plastic corners into the gap between the cylinlar and top strap. The indicated pressure was bstween 90#000 and 100,000 lbs./sq. in. The case remained intact showino no rupture marks whatsoever. Limited firing tests with the sabot-flechette assembly, fired in triple bore salvo with 57 grains of 2400 powder, show complete sabot disintegration "outside the bore within 20-30 feet. Observed patterns af 100 yards show a 3 to 5 mnl extreme spread. No strippers were used in any of these testa. (b) * AREA FIRE WEAPON In Phase I, the main emphasis of the area fire pxWotam was in ballistic tests to prove the basic reasoning that *:Lth th4!. low pressure type of ammunition, it is unnecessary to 'ave a reciprocating chambering system. It was believed that a simple repeating lauvcher mechanism could be designed as an attachment to the rifle, which would weigh between 1.0 and 1.5 lbs. Accordingly, a relatively thin walled plastic cylinlAdrsk adapter was machined-to contain the 40 =/a round. This was fired unsupported in a firing, fixture (see plate #10). It was found that the plastic adapter (weighing .03 lbs.) gave perfect obturation, and was capable of Withstanding several firings without any damage. In order to determine the effect of the lateral shift of the center of gravity on the center of impact, an M79 Launcher was fitted with an M4 Mortar Sight, to enable high Angle firing with shoulder. "" support. Steel weights were inserted into 40 n/a adapters and .i ENO A [ -. 0 I;' ', -- 6- • were taped to the side of the M79 to more than double the weight of the two rounds of 40m/rm ammunition which #ould extend from the side in the proposed design. Six shots were fired at a range of (see plate approximately 300 meters and the center of iippact noted. #11) The weights were then removed, and the launcher was again fired with six more shots at the same range and the same sighting point. There was no difference in the center of impact from the previous six shots. This indicates that the old T148 three chamber launcher showed a distinct pattern for each of the three shots for reasons other than center of gravity shift. It was found that the firing of plastic adapters with varying clearances around the 40 m/m projectiles, different patterns were obtained. It~was..also found that a closely controlled tight fit of the adapter and projectile, produces good accuracy. 6. Pr6posed H&R, A Inc. Development Plan. in Phase II It is expected that the first complete prototype of S.P.I.W. will be fabricated, assembled and tested during August 1963. It is contemplated that it will be tested at Aberdeen Proving Grounds during the last week of August, with the assistance of Ballistic Research Laboratory, Human Factors Engineerin(. Laboratory, and the Army Test and Evaluation Command. Following the initial test period, it is contemplated that all necessary redesign and refabrication of parts will take place during September and October. A second series of tests will then be conducted at Aberdeen with the assistance of the above mentioned agencies. Following the second series of tests- the ten (10) pro'totypes will be manufactured and test fired so as to effect delivery : by the middle of February, 1964, Ammunition development and testing will continue throughout the entire program so as to achieve optimum quality control on all components as well as ballistic uniformity. In view of the extremely encouraging results of firing tests obtained in Phase I, with both the point fire and area fire ammunition, and as a result of further study, this -ontractor believes that~a much more effective S.P.I.W. systea can be delivered in the same tiwe frame, (February, 1964) by expanding The scope of work in Phase II. This expanded scope cont~epl&ts the reduction in the size and weight of the complete weapon, by reducing the 1V%.NJJJ1JJJJJJJ~iJj IM -7- cross section of the present ammunition design. This will be investigated with both the present .217 sabot flachette assembly and with the sabotleas projectile of .125 diamet. , The reduction in ammunition cross section, reduccW the sixe of the Open Chamber Cylinder and ammunition storage wgazinat. a very significant extent. It is also proposed that an extensive ballistic test program sho-uld ber undertaken to prove out all basic components of the SaJvo Tround, such as the plastic case and beling, "under extreme temperature and storage conditions. Several mechanisms will also be investigated concurrently to permit optimum selection within the shortest time period. Al6ng with mechanism and ballistic developpments and tests, production studies will be conducted to minimuize the tiue perioci for actual "ur: production if, and when required, as well as establish production costs. Another area of investigation lies in the use of a significantly improved 40 m/m or 30 =/m projectile. Preliminary studies conducted by this contractor, and Pic~tinny Arsenal indicate the feasibility of developing a bQosted'Tacket projectile, in a relatively short time frame. This projectile would be encased in a cylindrical plastic container or cartridge case containing a small steel high pressure chamber, element. The terminal velocity of this projectile would be in excess of 800 ft./sec. which would make it effective against vertical targets -A 1000 meters instead of 100 meters as at present. The complete round would weigh substantially the same as the present 40 m/m rQund encased in the plastic adapter, and would be of approximately the same size. . ½*WI1S.15jm 1i.1 - , ,A 71