UNCLASSIFIED AD NUMBER

1 UNCLASSIFIEDAD NUMBERAD822736 NEW LIMITATION CHANGETOA pproved for public release, distributionunlimitedFROMD istribution authorized to Gov' only; Administrative/OperationalUse; 30 JUN 1967. Other requests shall bereferred to Commander, Army MaterielCommand, Attn: AMCPM-RS, Rock Island, ltr, 1 Mar 1968[per OCRD, D/A memo, 28 Mar 1968]THIS PAGE IS UNCLASSIFIEDAD>DRe::zt No. SA4114l-025 DEVLOPENTOF A STELL IT! -LINED * *BARUL FORDate 30 un19196 FAA% %immmitta1 of th~is doeument ouatsido thjigaoo of Govs~u,.nt must have prior ' 4 AftPM .)tS ARMORYSPRINGFIELD, MASSACHUSETTSBest Available CopyAVAUIBAIUITY ,fldrqu*ster,*, sain copies of tb report frau th findings in this report are not to be construed as an officialDepartment of the Army position unless so designated by other author-~Th cizedtdomntsn this report of trade names and manufactrers does notcontitteofficial indorscement or report is to be destroyed when it is re longer needed.

2 It is notto be returned to the to l ..REOT: SA-TR1-7025 DATE: 30 June 1967 AMCMS CODE: OF A STELLITE-LINED, CHRCIMIUM-PIATED BARREL MACHINE GUNT echnical ReportDA PROJECT TITLE: Small Arms Weapon Systems: Lined and Machine Gun BarrelsDA PROJECT: 1W523901A30408 This TECHNICAL report , to the extent known, does not contain anypatentable material, copyrighted and/or copyrightable -7025 ABSTRACTThe procedure as developed by Springfield Armory for design andfabrication of a stellite-lined, chromium-plated barrel for machine gun is described. Results of erosion tests of thestellite-lined barrels, standard barrels, and two other types ofbarrels show that the stellite-lined barrels are superior in ero-sion resistance. One of the stellite-lined barrels was fired43,994 rounds prior to rejection. A maximum of 12,476 rounds wasfired from one of the standard barrels prior to rejection. Thetwo other types of barrels -a standard barrel with a nitridedbore and a barrel of two-piece construction -were fired 29,874and 990 rounds, respectively, before rejection.

3 The two-piecebarrel has an 18-inch forward section made from Cr-Mo-V steeland the rear section, including the chamber, is made entirelyfrom stellite. All barrels were rejected on the basis of the pro-jectile instability criterion -15 degrees yaw of 20 per cent ofthe projectiles fired. All barrels were fired at an average rateof 200 shots per minute.(i)'I, of CoiclusionsRecommendat ions2 Introduction3 Materiel3 ProcedureDesign4 Development of Fabrication Techniques 5 Liner Assembly 6 Gaging 6 Teat8 Results and Discussion 9 APPENDICES 13A -Calculations 14B -Tabulated Data 24C -Photographs 26D -Drawings 33E -Distribution4K * Dstribtion40(ii)mamU IREPORTSA-TRI-7025 SUBJECTD evelopment of a Stellite-Lined, Chromium-Plated Barrel Machine GunOBJECTIVETo design, develop, and fabricate a lined and machine gun barrel for improved erosion life under extreme ratesof OF RESULTSOf the four types of machine gun barrels tested, the SpringfieldArmory 3-piece, stellite-lined barrel with chromium-plated bore gavesuperior erosion resistance.

4 Two barrels of this configuration, desig-nated Proto 1 and Proto 2, were rejected after 33,433 and 43,994 roundsrespectively, were fired. Rejection was based upon projectile instabilitycriterion of 15 degrees yaw in 20 per cent of the shots fired during atest cycle -in this instance, 40 shots out of 200 shots two standard barrels with nitrided bores were procured fromManufacturer X and were second in erosion resistance in that these barrelswere fired 29,874 and 26,774 rounds before rejection. These barrels weredesignated NI and N2, maximum erosion life of the standard unplated barrels in thistest was 12,476 rounds for Barrel Sll. Barrels 2, 3, 588, and 590B wererejected at 2509, 5088, 7116, and 4209 rounds, standard unplated barrels and the standard barrels vith nitridedbores were made from 4150 resulphurised -REPORTSA-TRi-7025 SUIMARY OF RESULTS -ContinuedBarrels 1, 2, 3, 542B, 588, 590B and Proto I were tested with bothball and tracer amuunition.

5 All other barrels were tested with ballammunition only. No definite conclusions can be made concerning theeffects of tracer ammunition upon barrel erosion life since this testwas not designed to evaluate the differences in erosion rates betweentracer and ball ammunition. Ruptured projectile jackets were encounteredwith the tracer ammunition. Figure 6, Appendix C, show that the jacketsare stripped while the projectiles are in barrel designated EXO01 was designed and fabricated by Manu-facturer X. This barrel was fabricated in two parts, an 18-inch forwardsection which was made from Cr-Mo-V steel and a rear section that includedthe chamber which was made entirely from stellite. This barrel was re-jected after 990 rounds of the schedule were fired. A past history of2000 rounds claimed by the manufacturer was not verified up to the timeof the completion of the of the barrel rejections were based upon the projectile insta-bility criterion.

6 None of the barrels exceeded the criterion of a lossof 200 feet per second or more in projectile velocity. The averagefiring rate used throughout this test was 200 shots per is recommended that barrel of the Springfield Armory prototypedesign be considered to replace present monobloc, unlined, unplatedbarrel used in the SAWS candidate machine December 1964, a comprehensive study of all rifles and machineguns either being used by or oe ng submitted to the field forces wasinitiated by the Army Materiel Co-mand. This study included aclass of weapons in which the cartridge is used. SpringfieldArmory's assignment in this effort was to test existing barrels and,if necessary, to develop a satisfactory barrel for military preliminary study on barrels showed that it would beextremely unlikely that a 4150 steel monobloc untreated barrel couldwithstand high temperatures and erosive effects of the propellant gasesin repeated firing of a machine gun in the field.

7 Sample calculationsshowing heat and stress in the barrel components during firing are shownin Appendix A. From these preliminary calculations, materials wereselected and physical dimensions were determined for the retainer, thetube, and the liner for a 3-piece barrel. Drawings for the barrel werethen prepared. Scaled-down prints of the detail and assembly drawingsare included in Appendix D. Gages and fixtures needed for fabricatingand inspecting components, assembling the liner, plating the bore, andfor proof-firing were designed and built at Springfield Cartridge -Livks~d Metallic Belt, 4 Ball, M153,1 Tracer, M196 Ammunition Lot. Ball Ra 5122; Tracer RA 5025 Test Receiver Assemblies. , , Coda X, with Trigger Assemblies,Serial Nos. 000565, 000578, 000588, 001169,001209, 001213, 002271-3-REPORTSA-TRI-7025 MATERIEL -ContinuedTest Trinaer Assemblies. Two, with Solenoid-Operated TriggersTest Barrels. Eleven barrels were procured from Manufacturer of these barrels -Nos.

8 1, 2, 3, 542B, 5880, 5908, 810, and 811were of the standard design and were made from 4150 resulphurised barrels -Nos. NI and N2 -were made from 4150 resulphurised steelwith nitrided bores. Each of these barrels was equipped vith a 3-positionrgas port adjustment valve. Barrel EX001 was made with a 2-piece con-struction, stellite breech threaded to an 18-inch Cr-Mo-V steel forwardsection. Barrels Proto I and Proto 2 were of the Springfield Armory3-piece design with Cr-Mo-V steel tube, 6-inch stellite liner, andCr-Mo-V steel retainer. The bores of these barrels, Proto 1 and Proto 2,were Electronics Counters Inc., Model 453, with Lumillne ScreensPROCEDURED esigno After a preliminary study of the potential firing schedules machine guns was made, a basic design was selected. The configura-tion of the design and the materials used in this design provided thegreatest resistance to the high temperature and erosive effects of thepropellant gases.

9 The selected design ws a 3-piece barrel which con-sisted of a 6-inch stellits liner, shrink-fitted into a chrome-moly-vanadiuatube and retained in position by means of a chrome-soly-vanadium retainer is threaded to the tube and is torqued in place. To obtainbetter wear and greater corrosive resistance, it was necessary to chramium-plate the bore of th4 tube to a thickness of .0005 to .0015 -7025 PROCEDURE -ContinuedThe design procedure vas as follows: The physical dimensions ofthe retainer, the tube, and the liner were determined. The designc6iteria used in the determination of these dimensions were based uponthe pressure and thermal stresses of the barrel components duringfiring. These procedures with sample calculations are included inAppendix A. These procedures are given in greater detail in Snainerin&Design Handbook: Gun Tubes, AMCP 706-252. Drawings were prepared onthe basis of the calculations. A compleLe set of drawings -detail,subassembly and assembly -are included in Appendix ,_ent of Fabrication processes and plating techniques for stellite-linedand chromium-plated machine gun barrels were previously developed atSpringfield Armory and were used in the manufacture of the M73,the M60, and the caliber.

10 50 M485 machine gun barrels. The basiccompoaaents for a barrel of the Springfield Armory design are the tube,the retainer, and the liner. The components for the barrel weremachined without difficulty even though the bore sie was consider4blysmaller than that of the production tube and the retainer were made from Craio-V steel and theliner was made from otellite. The bore surface of the tube was chromium-plated to a depth of .0005 to .0015 inch. Even though the chromaid-latingof a barrel bore of the 5.*5m caliber had been previously demonstratedo-5-oREPORTSA-TRi -7025 PROCEDURE -ContinuedDevelotment of Fabrication routine process had not yet been developed. Some experimunation inanode-sizing, anode holder design, and electrolyte-pumping rates wasrequired to establish the proper plating techniques for plating barrel the assembly of the liner to the tube requires a shrink-fitcondition, the tube must be heated prior to assembly of the liner.