Historical Document · 1974
AAI Corporation's final report of May 1974 under contract DAAF03-72-C-0172 on a simplified serial flechette rifle. The Hyper-Burst Mechanisms dive cites it for the AAI line between the SPIW and the ACR.
T ^7 o < £l INAL REPORT» / 7 ^> DESIGN AND DEVELOP / A I SIMPLIFIED |ERIAL FLECHETTE RIFLE# ——————J5 ••• a t!/ DAAEg3-72-C-^172 / / I Ti | HIT/ ER-7896 ! DEC 1 1i / / y May »74 / \ ^ Date ' /-» Approved fjr Public Release; Distribution Unlimited • m w ,a A )I I F / * -L < >r/f^>o^atLOM, |ir» •Ml ' (*. ö w 5to Boi M £ g ° ft if $ (JflpWtjatjuDMj / TABLE OF CONTENTS Title Page I. INTRODUCTION 1 II. SCOPE OF WORK 3 A. Design Study 3 B. Delivery Requirements 6 RESULTS OF INVESTIGATIONS 7 A. Trigger Group 7 B. Muzzle Device C. Stock II D. Heat Sink and Radiator 12 E. Ejector 20 F. Firing Pin 23 G. Maintainability 27 H. Reflex Colliroator Sight 29 I. 30ttm Launcher 36 J. Physical Characteristics 39 III. IV. . 10 CONFIGURATION BASE LINE 40 APPENDIX A - ANALYSIS OF FIRING PIN ENERGY iii A-l s I. O/ifH/taljLOW, INTRODUCTION Under Contract No. DAAF03-72-C-0172 with the U. S. Army Armaments Command, Rock Island, Illinois, AAI Corporation was to condm>t a research and development program for the purpose of simplifying the XM19 Rifle. The weapon configuration emanating from these efforts was identified as the XM70 Rifle. The program was divided into two phases - the first consisted of the research activity and the second the fabrication of two XM70 Rifles and associated ancillaiy equipment as per an approved Configuration Base Line (CBL). The effort was originally scheduled to be completed in a fourteen month time frame. Of this, ten months were provided for the design study and the remaining four months allotted for fabrication of the hardware. However, during the course of the program, the government modified the contract to expand the scope of work. The goal of the program was r.o, through simplification, offer a system with increased reliability and effectiveness while decreasing its weight and cost, wjhis was to be accomplished primarily through the following design changes. ^ *— A. Simplified Trigger Group B. Open Bolt Operation C. One-Piece Barrel D. Ammunition Design The following pages of this document contain a summary of the contract goals and requirements and describe this contractor's activities and achievements. Section II presents the contract scope of work and the physical C^Ot^C/tatLOU restraints and functional characteristics stipulated as requirements or guidelines for the XM70 system. The discussions in Section III provide a cursory review of the activities performed and the results of the associated ballistic tests conducted. Section TV is a tabulation of the drawings, with appropriate revision designation, identifying the components and assemblies which comprise the Configuration Base Line (CBL) for the XM70 Rifle. firing pin energy is presented in Appendix A. An analysis of the II. SCOPE OF WORK A. Design Study 1. Trigger Group a. Relocate sear for open bolt operation b. Redesign for semi-automatic and 3-round burst operation, In addition, provide one area fire mode. c. Incorporate necessary interchangeability features to accommodate closed bolt trigger group (i.e., XM19 mechanism) for closed bolt functioning. 2. Muzzle Device a. Investigate effect of aerodynamically stripped sabot on performance of muzzle device. 3. Stock a. 4. Redesign stock to facilitate the following: (1) Sight mount for collimator sight. (2) Ejection port cover. (3) Trigger group and heat sink modifications. Heat Sink and Radiator a. Consider elimination of radiator from system. b. Modify heat sink as necessary to fulfill needs of new system requirements. 5. Ejector a. Investigate approaches for reducing travel of spent cases. CjtrtpiyuitiiH*, 6. Firing Pin a. Evaluate effect of alternate firing pin teat configurations on the all-fire energy of the primer. 7. Maintainability a. Develop design modifications in the areas of the buffer housing, latch and guide rod assembly to simplify and ease field stripping. 8. Collimator Sight a. Design and manufacture two collimator sights with the following capabilities and features: (1) Compatibility with GFE optical components. (2) Provide for internal reticle adjustment and allow for + 2 mil adjustment after zeroing at 100 yards. (3) Sight shall be compatible with mounting provisions on XM70 Rifle. Mounting shall possess capability of retaining line of sight between sight and bore within 1 mil over a 1000 round firing schedule. (A) The mounting of the sight shall be such as to have an eye relief within the following limits . . . (5) (a) Five (5) inches - minimum (b) Seven (7) inches - desired (c) Ten (10) inches - maximum (required) the mounting of the sight shall be such that it is not necessary to remove for or inhibit field stripping. CjyipovutjjD WL 9. 30mm Launcher a. Design and manufacture a single shot, 30mm launcher to conduct test firings to ascertain feasibility of system integration. b. Prepare necessary drawings which show modifications to the XM70 Rifle to permit retrofitting of the launcher concept. 10. 11. * Physical Restraints a. Empty weight with 50 round magazine - 7.8 lbs max. b. Length ---------------- 42 in. ma\. c. Trigger Pull ------------- 4-6 lbs required d. Compliance with TDP CBL --------- Functional Characteristics a. Single shot accuracy (Machine Rest LSD) -------- mils max. avg. b. Three round burst extreme spread - - - mils max. avg. c. Noise (at Shooter's left ear) d. Reliability (malfunction rate) - - - - .57. required .37. desired e. Cyclic Rate f. Maintainability (Field Stripping) * - - - - 160 db max. ------------- Comparable to XM19 Rifle Values to be determined pending GFE ammunition performance. Co^oxatLow, B. Delivery Requirements 1. Two (2) XM70 Rifles 2. Ten (10) 50-round Magazines 3. Technical Data Package (CBL) A. Contract Data Requirements Per DD Form 1423 ® III. ( m!nir\oXkX)*> RESULTS OF INVESTIGATIONS A. Trigger Group The configuration of the trigger group assembly developed for the XM70 Rifle possessed a number of the basic operating concepts contained in its XM19 counterpart. Aside from relocating the sear to accommodate open bolt operation and utilizing a pulling type motion for the counting sequence in lieu of the original pusher system, no other significant design modifications were adopted. Since the automatic mode of fire was deleted, the mechanism could be simplified and a significant reduction in weight achieved. The photographs on pages 8 from both sides. rounds was and 9 are views of the mechanism At the conclusion of the test program a total of 5845 fired during which only one design modification was made. firing 3845 rounds, eight (8) miscounts were encountered. traced to an overstressed counter retainer spring. After The cause vas After replacing the subject spring with an improved design, an additional 1000 rounds was expended and no malfunctions were experienced. This is equivalent to an overall malfunction rate of 1.4/M. The following chart compares the salient features of the XM70 trigger group with its predecessor used in the XM19 Rifle. The greatest single factor contributing to the increased trigger pull is the higher drive spring force developed at the seared position when firing from the open bolt. From Appendix A, the spring deflect ionat the seared position in the closed and open bolt systems is 6.68 and 11.86 inches respectively. With (liyipcndtiJD*, &VC RIGHT SIDE TRIGGER GROUP ASSEMBLY p CMX^OXOÜJD M, <*'•: VQ LEFT SIDE TRIGGEK CROUP ASSEMBLY (^OtfjOtotLOW, a spring rate of 2.2 lbs/in the corresponding forces are approximately 19 pounds in the XM19 as compared to 26 pounds in the XM70 Rifle. Comparison of Trigger Mechanisms Characteristic XM70 XM19 Modes of Fire Semi-Automatic 3-Rd Controlled Burst Semi-Automatic Full Automatic 3-Rd Controlled Burst Weight .46 lb .82 lb No, of Parts Al 58 Trigger Pull 14 lbs 9.3 lbs* * Based on the results of tests perfomed on the wea, ons fabricated on Contract No. DAAF03-71*C-0281. B. Muzzle Device The configuration of the muzzle attachment supplied on the XM70 Rifle was essentially identical to that employed with the XM19 weapon. Minor modifications were made to certain components to compensate for diiiicnsional differences between the one-piece barrel and the previous barrel barrel extension assembly. Also, with the advent of the collimator sight the front sight was removed from the muzzle device. Because the test weapon was used extensively for heat tests, the barrel bore was severely eroded and considerably oversize. Because this condition can produce "slips" - abnormally low muzzle velocities, when launching the flechettes, accuracy tests were not conducted with the 10 Cö'tpO'LatiLOM, aerodynamically stripped sabot cartridge. Therefore, investigations to determine if compensation related revisions would be required were not conducted. The propellant loaded in the cartridges to be u9ed in the government evaluations of the weapon system is very similar to that contained in the XM645 cartridge. Also, the charge weight has been reduced. Conse- quently, it is believed that noise and flash levels will remain within acceptable levels. C. Stock The configuration of the stock selected for the XM70 Rifle was established from parallel investigative efforts conducted on this contract and Contract No. DAAF03-71-C-0334. Under the subject contract the guidelines for the stock design were dictated by requirements for interfacing with the collimator sight mount, incorporating an ejection port cover and modifications emanating from relocating the trigger group assembly. Also, inputs were obtained from the heat tests - elimination of the radiator, changes in the envelope of the heat sink and the addition of a deflector, which contributed to the ultimate configuration of the stock. Concurrent with the above efforts, a number of studies were performed on Contract No. DAAF03-71-C-0334 which were instrumental in determining other features of the stock. From these paper investigations such concepts as combining the foregrip with stock and extending the magazine well to provide added support were adopted. The collimator sight with its higher line of sight necessitated raising the cheek rest area of the stock to provide a comparable eye level for aiming. 11 Changes were made in the hand (ZoxpcnatjuD*. grip area to improve structural Integrity and general handling characteristics. Ribbed projections, located on each side of the stock, aid in preventing the gunner from contacting the barrel cover or inadvertently inserting his fingers into the holes. To facilitate field stripping, the upper portion of the stock in the area of the foregrip was attached as a separate piece. This part, identified as the barrel cover, prevents the gunner from accidentally touching the barrel or heat sink and is affixed to insulators at each end. The final configuration of the stock and barrel cover, fabricated on Contract No. DAAF03-71-C-0334, is in accordance with Dwg. No. 53099-41008, Rev. B and 53099-41129 respectively. They are shown pictorally on pages 13 and 14 . D. Heat Sink and Radiator One of the objectives of the program was to eliminate the radiator and redefine the requirements for the heat sink. Since the weapon operates from the open bolt position, the cook-off problems associated with the XM19 Rifle were eliminated. Now, the controlling factor, aside from the human engineering aspect, was the temperature attained by the barrel. The barrel blanks supplied by the government were made of AISI Type Hll material, heat treated to an average hardness of R equivalent to a yield strength of 125,000 psi. 35. This is The information on page 16 is a graphical representation of yield strength versus temperature for the 4140 material used for the XM19 barrel and two candidate materials, Inconel 718 and AISI Type Hll, under consideration for use with the XM70 Rifle. 12 To Ct/tp&uifijD VL DC U n Cjo^ixyiäGjDiAj a- S5 C H 3 w Ö E H H tu PS lg ü <A \l* A Co»i|)o%dtLoWi illustrate the influence of hardness, two graphs are presented for the Hll material. The data used to generate the curves for Hll steel was extracted from MIL-HDBK-5A, "Metallic Materials and Elements for Aerospace Vehicle Structures". The table below compares the values of yield strength based on exposure to the temperatures listed for up to 1/2 hour. Figure 2.5.1.2.1(b) of the aforementioned reference provides the percent reduction in the ambient temperature yield strength at these temperatures for this exposure time. Effect of Temperature on Yield Strength of Hll Material Temperature | 7. Reduction In Y eld Strenj Yield Strength, psi R 35 R 56 c c 70 0 125,000 243,000 200 97 121,000 236,000 400 92 115,000 224,000 600 87 109,000 211,000 800 80 100,000 195,000 900 73 91,000 178,000 1000 65 81,000 158,000 1100 50 63,000 122,000 For these tests, the Inconel 718, one-piece barrel supplied by the government was assembled to the test weapon. of .2271 inch and a hardness of R c It had a nominal bore diameter 42. To establish a basis for any subsequent investigations the radiator and heat sink were removed. An .032 inch thick, polished aluminum shield was installed between the barrel and bottom of the foregrip. 15 The OrtfKJtdtlOK/ 16 OytfKAiätioH, top of the foregrip was replaced with a metallic mesh material to increase the venting area. A pad of asbestos insulation was inserted between the sight mount and the outside diameter of the barrel to reduce the heat flow to the sight housing and optical components. tabulated at the top of page 19 . The results of this test are Note that, with this limited firing schedule, the temperature measured at the critical location - 4 inches forward of the chamber, exceeded 1200 F. Since it was impossible to predict the pressures developed at these temperature levels, and, in view of the adverse effect of temperature on yield strength, it was dec'ded to terminate the test. Based on these findings, a 1/2 pound heat sink was fabricated and assembled on the weapon. The sink, shown in Figure 1, is press-fitted onto the barrel in the area immediately forward of the sight mount. The schedule for the second test was predicated on firing until a temperature of 1200 F was reached at the mid-barrel location. The test was terminated when the area of the foregrip adjacent to the front radiator ignited. However, at this point, a total of 550 rounds was fired and the temperature reached 1100 F. The rate of fire for this test averaged 96 rounds per minute. A summary of the data generated from this second test is presented at the bottom of page 19 . The historical record of the temperatures monitored at the four locations during the two tests is shown graphically on page 21 and 22. As mentioned earlier, the barrels for the two XM70 Rifles were fabricated from the Nil material. The data on page 15 indicates the yield strength of this material at 1100 F is 63,000 psi. 17 Regardless of the (\j?xp<yuitjuDK* o <5 < 1 } 111 • < 0 k U UJ ^ s Ul >) <* & H V) V ^ <o k * Ui ^t 18 0 Cjo^cndSjuofAj Results of Heat Tests Test #1 - W/0 Heat Sink and Radiator A total of 200 rounds was fired in 98 seconds (120 rounds/minute) Location Temperature. Sight Mount 200 Chamber 325 Mid-Barrel * 1185 Muzzle Device ** 1455 "F Test #2 - W/.54 lb. Heat Sink but v/o radiator A total of 550 rounds was fired in 344 seconds (96 rounds/minute) Location Temperature, F After 350 Round 8 After 550 Rounds Sight Mount 105 130 Chamber 355 404 Mid-Barrel * 915 1100 Muzzle Device ** 1560 1660 * At Point 4M Forward of Chamber ** On Barrel, Inside of Muzzle Device Chamber 19 7 exposure time, up to 1000 hours, no data was presented beyond 1100 F. Whether this implies that the test was terminated at this point or the material exhibited no measurable strength at higher temperatures is not known. Hence, to provide some safe operating margin, it is recommended that the firing schedule for the XT-f70 Rifle be limited to 100 rounds per minute for a period of 3-1/2 minutes (350 rounds). Rased on this the temperature developed at the critical mid-barrel location should be approximately 915 F. At this temperature, the graph on Page 16 indicates the corresponding yield strength is approximately 90,000 psi. E. Ejector In this area of investigation the effort primarily addressed the feasibility of utilizing a spring loaded system as a method by which the ejection pattern of the expended cases could be altered. The fixed ejector design used in the XM19 Rifle generally propels the cases to the right, rear of the gunner to a distance of approximately 30 feet. Independent investigations by this contractor and Rock Island Arsenal indicated that the response time of a spring mechanism would be too slow. By the time the spring reacted to absorb any appreciable amount of energy, the case will have been ejected with no noticeable change in the pattern characteristics« However, a second approach evaluated considered using the ejection port cover in a dual role - to cover the breech area and as a castdeflector. A projection was added to the underside of the cover vhich 20 «I r r i r~ i « » • Co'lpO'LottOM, engaged the case as it pivoted from the face of <e bolt. The subsequent contact redirected the spent case in a slightly forward and dovmward trajectory. It is estimated that the cases travel about 10 feet when firing from the standing position. The configuration of the ejection port cover is shown in Figure 4. While test data as to the reliability and functional characteristics of this approach is limited, it was decided to incorporate this feature in the ejection port covers provided on the delivered weapons. Engineering tests of the XM70 Rifle scheduled by the government can be used to determine the acceptability of the design. In the event problems are encountered, it is a simple operation to remove material from the cover and permit the cases to eject unimpeded. F. Firing Pin In an effort to further supplement the improved ignition characteristics anticipated as a result of the increased firing energy available when firing from the open bolt, investigations were conducted to examine experimental firing pin teat configurations. The goal was to achieve a reduction in the all-fire energy requirements of the piston primer. tip shapes tested are depicted in Figure 5. The two candidate Both of the designs feature spherical radiused tip contours to prevent the occurrence of pierced primers. Also, the maximum protrusion of the teat from the face of the firing pin was Increased in an attempt to obtain greater penetration. In addition to the piercing problem, a second factor that controls the teat configuration is the elongation of the web. to R c With the present material, 1065 steel, heat treated 32-36, the maximum elongation is approximately 13 percent. 23 °" " -- * I'll Hi IM = Cxnp&w£t> H/ I at o u DC 2 £ 55 O M -«:; 60 -H tu C&tporuätijDH, (A H H i O in o B r es w 25 Ü M Ctytp€yujfiuD*j The results of the sensitivity tests disclosed that the experimental shapes, based on the frequency of misfires, lessoned system sensitivity. While the depth of penetration was always greater with the experimental designs at a given input energy, jntil the energy exceeded 60 inch-ounces, a greater volume of composition was displaced by the standard teat configuration. This tends to lend credence to the theory that increased intergranular movement is beneficial to ignition characteristics. Based on these findings and the higher firing pin energy that will be afforded by open bolt operation, further inve tigation did not seem warranted. To compare the firing pin energy of the XM70 Rifle with its predecessor, the XM19 Rifle, the analyses presented in Appendix A was performed. It utilized data generated from actual testing of the weapon during the development of the drive spring system and from information provided by evaluations at PKL. the table below. The results of this analytical review are summarized in It is immediately apparent that the XM70 system offers significant increases in firing energy which should contribute markedly to the reduction in the number of misfires experienced. COMPARISON OF FIRING PIN ENERGY FROM THE SEAR POSITION After 6000 Cycles (in.oz. ) New Drive Weapon Spring (in.oz.) New Spring After 6000 Cycles XM19 155 *** 94 * 12.0 9.6 XM70 485 ** 163 ** 21.8 12.6 * ** •** Measured - See Table 4 in ER-6571. After actual losses incurred as determined from T-D curves recorded at BRL Obtained by subtracting the energy loss of 69 inch-ounces (Table 4 of ER-6571) from the original energy of 224 inch-ounces when the spring was new. 26 X Firing Pin Velocity (ft/sec) , rt. Confxrtotboii G. Maintainability Field reports received from personnel involved in the testing of the XM19 Rifle at Ft. Ord, California during Experiment 21.9 indicated difficulties were being encountered during field stripping operations. The problems were traced to the following items: 1. Difficulty in removing the buffer housing. 2. Misalignment in the tip area of the guide rod assembly. 3. Inadvertent rotation of the radiator. In reviewing comments regarding the first of these items, it was learned that gripping the housing and manual retention of the partially compressed drive spring were the major factors contributing to this problem. To ease the removal of the buffer assembly, the projections on the sides of the housing were enlarged to facilitate gripping. Secondly, a feature was added whereby the guide rod assembly is independently supported once it is in position to permit removal of the buffer assembly. By manually exerting a force in a forward and downward direction while pushing the guide rod assembly forward, the buffer lock will drop into a recess provided in the top surface of the receiver. A locking notch on the rear side of this recess engages a mating edge on the rear of the buffer lock. The lock is retained in this position by the force of the compressed drive spring. Hence, it is no longer necessary for the gunner to manually overcome this force while holding the guide rod assembly and removing the buffer assembly. To reassemble, simply reverse the sequence of operations. This locking feature is depicted in Figure 6. 27 ------ - .. C&tfM/lOitLOtl GUIDE ROD ASSEMBLY BUFFER HOUSING LOCKING SURFACE ASSEMBLED POSITION FORWARD LOCKED POSITION FOR WEAPON DISASSEMBLY BUFFER LOCK FIGURE 28 6 CxrtptytxdjuoM, The second item, misalignment of the guide rod assembly is, in general, caused by accidental rotation of the tip. Since the assembly pro- cedure prevents visual observation of the tip, it was necessary to insure that the concept selected would provide automatic control of the alignment. To accomplish this}a tab, or key, was added to the tip which nested in notches in the guide rod. To prevent disengagement of these interlocking projections, a self-locking cap screw was used. Figure 7. This design is shown in Since the radiator has been removed in the XM70 Rifle, problems associated with it's movement no longer exist. The sequence of operations required to field strip the XM70 Rifle is identifical to those employed with the XM19 weapon. The photograph on page 31 shows a completely field stripped XM70 Rifle. H. Reflex Collimator Sight One of the major design features of the XM70 Rifle was the use of a reflex collimator sight in lieu of the conventional metal peep sight arrangement. The envelope of the sight was controlled by the optics supplied by Frankford Arsenal. The design provides for internal retical adjustment with a total movement in elevation and azimuth of 11 mils. A tridium light source is used for nightime applications. The factors which were instrumental in establishing the position of the sight included the requirement to permit field stripping without disturbing the sight. * Also, the structural integrity of the mount and overall system weight were considered. Regarding the first item, it is highly questionable that the mount could be attached to the receiver and not interfere 29 Co^M/LOitLOM/ f GUIDE ROD ü KEYWAY GUIDE ROD TIP TT^ EH \\\\\N KEY N0.6-32XI/2 LG SELF LOCKING CAP SCREW V GUIDE ROD ASSY SCALE 2/ GUIDE ROD TIP FIGURE 7 30 Co*Cf>OXotLOM/ s Of H 9 SIn 31 • •••111! CotpOt/ÄttOIC with field stripping without increasing the complexity of the mechanism and decreasing reliability. Furthermore, it appears impossible to attach the mount to the receiver without effecting the interface between the stock and weapon and compromising the load carrying capability of the stock. To prevent egress of the spent cases from the breech and not impede the movement of the charging handle , mounting to the receiver is restricted to the left side. Consequently, it was decided to press-fit the mount onto the barrel immediately forward of the receiver. To minimize the length of the cant«levered mount, the sight was located to provide an eye relief of 10 inches. the mount. Also, the shorter beam minimizes the weight of As presently configured, the sight and mount weigh .71 and .16 pound respectively. One of the functional specifications of the sight/mount relationship required that the line of sight between the sight and bore be retained within 1 mil during a 1000 round firing schedule. To record any relative movement, the optical arrangement sketched in Figure 8 was developed. Mirrors were attached to the sighting fixture and weapon to provide reference points and insure the weapon is positioned uniformly in the set-up. Additional mirrors werebonded to the top and side of the sight mount and housing to monitor movement in these components. marked on the witness panel. The zero position of the reticle was By recording the changes in the location of the light reflected from these mirrors, it was possible to ascertain whether the movement, if any, was produced by optical or mechanical factors. 32 4 Co^o^atLoM/ SIGHT CHECK MIRROR WEAPON REFERENCE MIRRORS OPTICAL TEST SET-UP FIGURE P 33 -" • * X* Mim CotpOtOLtJLOM. The test program consisted of conducting the firing schedule tabulated in the following chart. Including the zero position, measurements were made of reticle movement seven times during the exercise. noted that for the first 200 rounds fired the reticle was fixed. It should be The maximum radial displacement of the reticle from its zero position was .213 mil. is considerably within the 1 mil requirement. An external view of the reflex collimator sight is shown in the photograph on page 35. Results of Tests to Measure Relative Movement Between Boresight and Line of Sight No. of Rounds Fired Radial Displacement, R (mils"* 100 R • .120 h • .213 3 = .160 • .160 l 200 300 R 500 \ 700 R = .160 1000 R • 5 6 34 This .160 Cjytp&ijätLoMj oHtu t -1 —' 8 w E n _: •_ ^ Co^oxdtLo *c I. 30MM Launcher One of the requirements of the scope of work was to design and fabricate a single shot, 30mm launcher mechanism that could be attached to an XM19 Rifle with a modified stock. The purpose of this effort was to conduct a series of firings whereby the stress developed in.the stock could be monitored and a determination made relative to the strength capabilities of the stock. The firing fixture was designed to insure that, when assembled to the rifle, the recoil forces would be imparted directly to the stock. The overall test set-up is depicted in the photograph on the • following page. A total of five cartridges from Lot MHR1-1, 07-73 was fired « for these evaluations. In an effort to record the extremes in loads imparted to the stock, firings were made with both fully loaded and empty magazines. The following chart contains data relative to the cartridge and firing mechanism. i Cartridge Weight 43 lbs Projectile Weight 38 lbs 30mm 3arrel Weight 84 lbs 30mm Magazine Weight ... .21 lbs 30mm Breech Weight 71 lbs Total Weight of launcher . 1 76 lbs Instrumentation consisted of recording muzzle velocity, taking highspeed movies and measuring the stress levels at four .'elected locations. Prior to attaching the strain gages, a coating was applied to the entire stock which, After firing, identified the pattern and location of the stresses developed. This aided in positioning the strain gages. monitored at the following locations: 36 The stresses wer? ClxyipoxäljuDH, H W co H B p5 O r iA_ • iMiMi— aii> 11 . - • - - CfrtfKrtxxXLOM/ 1. Top, right side of hand grip 2. Left side of stock, over the trigger and near the bottom of the stock 3. Right side of stock just below sear pin boss 4. Left side of stock just aft of launcher/stock interface With the mechanism loaded with three cartridges, the maximum stress attained was approximately 11,000 psi. 3y comparison, with an empty magazine the stress level reached 29,000 psi. The highest stress was at Location No. 4. Since the barrel was not rifled, friction losses were virtually eliminated. This accounted for the higher than normal muzzle velocity which averaged 303 ft/sec. The daca from the test is tabulated lr the chart below. Results of Launcher Tests Round Maximum Strain - u, € Charnel Channel Channel Channe1 No. 2 No. 1 No. 3 No. 4 No. Muzzle Velocity (fP8) 1 NR NR NR NR NR Used weighted dummy magazine 2 292 500 600 800 =^7000 Used weighted dinreny magazine 3 304 NR NR 1000 >14030 Used empty dummy magazine 4 315 700 NR 1000 18000 Used empty dummy magazine 5 302 600 >3000 1000 18000 Used empty dummy magazine Avg. 303 - - - * NR - No Record 38 Remarks OrtpO'UxtLOM/ A comparison of the launcher weights of the AAI test device and the Rock Island Arsenal semi-automatic mechanism disclosed the following correlation. The weight of the fully loaded AAI mechanism and an empty PTA multi-shot launcher are essentially the same. Based on this it is estimated that the maximum stress produced in the stock when firing the RIA semi-automatic configuration with an empty magazine will be comparable in magnitude to that obtained when firing the fully loaded AAI test mechanism * approximately 11,000 psi. At this stress level the stock design provides a substantial margin of jafety. J. Physical Characteristics 1. 2. Weight Rifle, empty -------------- 7.5 lbs Rifle, w/loaded 50 round magazine - - - 8.6 lbs -------- 42.5 in. Force required to pull trigger ----- 14 lbs Length Overall length of rifle 3. Trigger Pull - 39 1 Co^)0*totLOK/ A j IV. CONFIGURATION BASE LINE The Configuration Base Line (CBL) for the XM7C Rifle is in accordance with the Technical Data Package as described by the list of drawings tabulated on the following pages. . 40 N Co^poxatLoM. LIST OF DRAWINGS CONFIGURATION BASE LINE FOR XM70 RIFLE Dated: 30 March 1974 Drawing Title Drawing No. Revision 53099-41001 None Weapon Assembly, XM70 -41002 A Stock Assembly -41003 None Barrel/Receiver Assembly -41004 None Bolt/Extractor Assembly -41005 None Buffer Housing Assembly -41006 None Drive Spring Assembly -41007 A Trigger Group Assembly -41008 C Stock, Gun, Shoulder -41009 None Maintenance Kit Assembly -41010 None Selector Lever Assembly -41011 None 50 Round Box Magazine Assembly -41012 None Sling Assembly -41013 None Firing Pin -41014 A Handle, Charging -41015 None Cleaning Rod, Maintenance Kit -41017 None Oil Container, Maintenance Kit -41018 None Cap, Maintenance Kit -41019 None Oil Dabber, Maintenance Kit -41020 None Patch Container, Maitenance Kit -41021 None Tool Holder, Maintenance Kit -41022 None Patch Tip, Maintenance Kit -41023 None Brush, Maintenance Kit -41024 A Extractor -41025 None Extractor Plunger -41026 None Spring, Compress ion,Extractor A Bolt Sleeve 53099-41027 41 Cjorxjp&wSjuD*, LIST OF DRAWINGS (continued) CONFIGURATION BASE LINE FOR XM70 RIFLE Dated: 30 March 1974 Drawing No. Revision Drawing Title 53099-41028 None Buffer Housing -41029 None Buffer Spring -41030 None Drive Spring, Single Strand -41031 None Drive Spring, Tri-Strand -41032 None Slide, Charging -41033 None Guide Rod Weldment -41034 A Buffer Lock -41035 None Guide Rod -41036 None Guide Rod Tip -41037 None Follower, 50 Round Magazine -41038 None Rivet, Box Magazine -41039 None Bottom Cover, Box Magazine -41040 None Spring, Box Magazine -41041 None 50 Round Box Magazine Weldment -41042 B P.F. Actuator Lock -41043 B Counter Puller -41044 A Counter Retainer -41045 B P. F. Actuator Arm -41046 B Sear -41047 None Shaft, Counter -41048 C Trigger -41049 A 30mm Actuator Lock -41050 A Operator -41051 B Selector -41052 B Housing-Trigger, Left Side 53099-41053 B Housing-Trigger, Right Side 42 0/I{>O*U£CLOK, LIST OF DRAWINGS (continued) CONFIGURATION EASE LINE FOR XM70 RIFLE Dated: 30 March 1974 Drawing No. Revision 53099-41054 A Pins -41055 None Bushing -41056 None Safety Spring, Helical Torsion -41057 A Counter Spring, Helical Torsion -41058 A Trigger Guard -41059 None 30mm Actuator Arm -41060 A Pin, Counter Puller -41061 None Seal, Side -41062 None Boot, Trigger Housing -41063 A Counter -41064 C Safety -41065 None Pin, Actuator Lock -41066 A Sight Mount -41067 B Retainer -41068 B Spacer -41069 B Cell -41070 A Retainer, Rear Window -41071 A Retainer, Reticle Assembly -41072 A Frame, Reticle -41073 A Sleeve -41074 None Spring, Compression -41075 F Shield -41076 None Screw, Pivot -41077 None Screw, Self-Sealing -41078 None Washer, Spring A Detent, Reticle Adjustment 53099-41079 Drawing Title 43 •MENMMMMtfVteMMMMMl Co*tf>o*tatJu>w, LIST OF DRAWINGS (continued) CONFIGURATION BASE LINE FOR XM70 RIFLE Date: 30 March 1974 Drawing No. Revision 53099-41080 A Cover -41081 None Pad -41082 B Mirror Mounting Plate -41083 A Retainer -41084 A Knob, Reticle Adjustment -41085 A Cover, Reticle Adjustment -41086 A Mirror, Bonded -41087 None Cell Assembly -41088 B Housing, Main -41089 None Reticle Assembly -410% None Cover Assembly -41001 A Sight, Reflex, Assembly -41092 None Sight, Reflex, Installation -41093 Sht 1-B Slit 2-A Receiver -41094 None Barrel -41095 None Ejector, Fixed -41096 B Insulator, Front -41097 None Swivel Assembly -41098 None Pin, Muzzle Device -41099 A Front Radiator -41100 None Insert, Muzzle Device -41101 None Muzzle Device Assembly -41102 None Plates; Vane, Rear -41103 A Plug, Muzzle Device None Bottom Plate, Muzzle Device 53099-41104 Drawing Title 44 Co^f>o\oltoK/ LIST OF DRAWINGS (continued) CONFIGURATION BASE LINE FOR XM70 RIFLE Dated: 30 March 1974 Drawing Title Drawing No. Revision 53099-41105 None Cone, Muzzle Device -41106 None Chamber, Muzzle Device -41107 Front Plate, Muzzle Device -41110 A A A A -41111 None Bushing, Butt Plate -41112 None Spring Stop, Butt Plate -41113 None Spring, Compression, Butt Plate -41114 None Pin, Sear -41115 None Plunger, Sear Pin -41116 None Selector Lever -41117 None Detent, Selector -41118 None Plunger, Selector -41119 None Tie Strap, Muzzle Device -41120 B Latch, Magazine -41121 None Sear Stop -41122 None Spring, Compression, Counter Puller -41123 None Spring, Compression, Operator -41124 A Spring, Compression, Counter Retainer -41125 None Spring, Compression, P. F. Actuator Lock -41126 None Pin, Guide - Counter Retainer Spring -41127 None Counter Retainer Assembly -41128 B Case Deflector and Dust Cover -41129 None Barrel Cover B Heat Sink -41108 -41109 53099-41130 Pad, Butt Plate Plug, Stock Butt Plate 45 0)*<|)C/U*IJLOW/ LIST OF DRAWINGS (continued) CONFIGURATION BASE LINE FOR XM70 RIFLE Dated: 30 March 1974 t • •; Drawing No. Revision Drawing Title 53099-41131 None Insulator, Rear -41132 A Spring, Case Deflector and Dust Cover -41133 None Pin, Case Deflector and Dust Cover -41134 None Insulator, Sight Mount -41135 None Heat Shield 53099-41136 None Nameplate, XM70 46 m Co^oxatLoM/ APPENDIX A ANALYSIS OF FIRING PIN ENERGY A-l Con|)o%atu)M/ For the present XM19 weapon Free length of drive spring = 18.21" From pg. C-10 Installed length (at battery") = 10.30" of ER-6571 Spring deflection @ battery, x. *Spring deflection @ buffer, = 7.91" x^. = 7.91 + 4.06 = 11.97" From data shs?et on page C-10 of ER-6571 the spring rate, K. is 2.2 #/in, Hence, the useful spiing energy is E s=2K[(xbUf)2- <*b.t>23 9 9 2 ? ^rcii.97) - (7.91)*] • 1.1(143 - 63) - 88 in-lbs The energy required to compress the buffer spring .08" is Where: •w * 2 K (x)2 K «= 2000 lbs/in = ^~ (.08)2 = 1000 x .0064 = 6.4 in-lbs Hence, the total available energy to the firing pin is E, - E + Ev , - 88.0 + 6.4 » 94.4 in-lbs fp s buf From T-D curves obtained at BRL during the drive spring study (see pg. C-12 of ER-6571) the velocity at battery was VL - 24.6 ft/sec bat * This consists of 3.98" firing pin travel plus an estimated .08" compression of the buffer spring. A-2 Cjo*p€rwtjuo *c Therefore, the kinetic energy was KE - jMV2 - jx 5—Y (24.6)2 x 12 * 38.6 in-lbs Hence, the losses in firing pin energy in traveling from the compressed buffer position to battery are E, * Ec - KE = 94.4 - 38.6 = 55.8 in-lbs L fp This represents 597. of the original energy. With the open bolt system, the firing pin will travel 3.95 inches from its seared position to battery. Since it will be seared in the SA mode and prior to firing the first round of a 3-round burst, any input energy from the buffer spring must be omitted. Therefore, the available energy in the firing pin will be that provideu by the spring alone or E, fP » 7 K [(x 2 sear )2 - (x, „)2 ] bat - j x 2.2 :(11.86)2 - (7.91)2] 1.1 (141 - 63) » 86 in-lbs Assuming equivalent losses, the available energy at battery will be L «E. - E « 86 - 55.8 - 30.2 in-lbs bat fp L or approximately 485 inch ounces. A-3 O/I^OfXxlJLOK/ The firing pin velocity would be « 2 32.2 x 30.2 x 2 ,„ V = r. rr = 4/5 fp .34 x 12 V. = 21.8 ft/sec *P It should be noted that these energy levels are based on a new drive spring. The energy to the firing pin in the XM70 rifle aft^r 6000 cycles was determined as follows. From Table 4 on Page 14 of ER-6571, the spring energy from sear to battery for the XM19 rifle was 163 inch ounces. As a new spring, the energy was E = ^k [<x )2 2 sear (JL oat )2] »|x2.2 r<8.68)2 - (7.91)2] E = 1.1(75.5 -63) 16 = 1.1 x 12.5 x 16 = 220 inch ounces Based on the reduced value of 163 inch-ounces, the spring deflections at battery and «ear in the XM19 rifle were determined, 'iecause of the permanent set in the spring, the actual spring deflections at these positions will be less. Free Length -» .77 (XMW 3.95 <XM70) sear A -4 bat C&tp&UitÄJDVL For the XM19 Rifle, E0 n = T K[ (X )2 - v(X. )2] • X X. . + .77 S-B 2 sear bat J) sear = bat 1634x2.2[(Xbat + .77)2 - (X^)2! x 16 163 = l.l[(Xbat)2 + 1.54 Xbat + .59 - (X^)2] x 16 163 = 1.1(1.54 3^ + .59)16 163 = 27.1 X, ,. + 10.A bat \at 152.6 27.1 X = 6.40" = 5.63" Therefore, X sear sear for the XM19 =• 5.63 + 3.95 = 9.58" for the XM70 Comparing 5.63" to the deflection of 7.91" at battery when the spring was new, indicates a set of 2.28" and a