UNCLASSIFIED

AD NUMBER

AD822736

NEW LIMITATION CHANGE

TOApproved for public release, distributionunlimited

FROMDistribution authorized to U.S. Gov't.agencies only; Administrative/OperationalUse; 30 JUN 1967. Other requests shall bereferred to Commander, Army MaterielCommand, Attn: AMCPM-RS, Rock Island, IL61201.

AUTHORITY

D/A ltr, 1 Mar 1968[per OCRD, D/A memo, 28Mar 1968]

THIS PAGE IS UNCLASSIFIED

AD

>DRe::zt No. SA4114l-025

DEVLOPENTOF A STELL IT! -LINED * CHRC1M-TZl.LD *BARUL FOR

Date 30 un19196

FAA% %immmitta1 of th~is doeument ouatsido thjigaoo of thiU.S Govs~u,.nt must have prior approvalo

.47TAO.' 4AftPM .)tS 04tAV.40.L

SPRNGFELD ARMORYSPRINGFIELD, MASSACHUSETTS

Best Available Copy

AVAUIBAIUITY NOTICE.

Qua ,fldrqu*ster,*, sain copies of tb report frau th ease

DISCLAIMERS.

The 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 approval.

DISPOSITION INSTRI3CTIOINS.

This report is to be destroyed when it is re longer needed. It is not

to be returned to the originator.

i to l .......

REOT: SA-TR1-7025

DATE: 30 June 1967

AMCMS CODE: 5523.11.45808o08.01

DEVELOPMENT OF A STELLITE-LINED, CHRCIMIUM-PIATED BARREL FOR

5.56141 MACHINE GUN

Technical Report

DA PROJECT TITLE: Small Arms Weapon Systems: Lined and Plated

5.56m Machine Gun Barrels

DA PROJECT: 1W523901A30408

This TECHNICAL REPORT, to the extent known, does not contain anypatentable material, copyrighted and/or copyrightable materials.

REPORTSA-TR1 -7025

ABSTRACT

The procedure as developed by Springfield Armory for design andfabrication of a stellite-lined, chromium-plated barrel for the5.56mm 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. 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,

REPORTSA-TR1-7025

CONTENTS

tug.Abstract

Subject1

Objective

Summary of Coiclusions

Recommendat ions2

Introduction3

Materiel3

Procedure

Design

4Development of Fabrication Techniques

5Liner Assembly

6Gaging

6

Teat8

Results and Discussion 9

APPENDICES 13

A - Calculations 14

B - Tabulated Data 24

C - Photographs 26

D - Drawings 33

E - Distribution4K * Dstribtion40

(ii)

mamU I

REPORTSA-TRI-7025

SUBJECT

Development of a Stellite-Lined, Chromium-Plated Barrel for

5.56mm Machine Gun

OBJECTIVE

To design, develop, and fabricate a lined and chromium-plated

5.56mm machine gun barrel for improved erosion life under extreme rates

of fire.

SM41ARY OF RESULTS

Of the four types of machine gun barrels tested, the Springfield

Armory 3-piece, stellite-lined barrel with chromium-plated bore gave

superior erosion resistance. Two barrels of this configuration, desig-

nated Proto 1 and Proto 2, were rejected after 33,433 and 43,994 rounds

respectively, were fired. Rejection was based upon projectile instability

criterion of 15 degrees yaw in 20 per cent of the shots fired during a

test cycle - in this instance, 40 shots out of 200 shots fired.

The two standard barrels with nitrided bores were procured from

Manufacturer X and were second in erosion resistance in that these barrels

were fired 29,874 and 26,774 rounds before rejection. These barrels were

designated NI and N2, respectively.

The maximum erosion life of the standard unplated barrels in this

test was 12,476 rounds for Barrel Sll. Barrels 2, 3, 588, and 590B were

rejected at 2509, 5088, 7116, and 4209 rounds, respectively.

The standard unplated barrels and the standard barrels vith nitrided

bores were made from 4150 resulphurised steel.

-l -

REPORT

SA-TRi-7025

SUIMARY OF RESULTS - Continued

Barrels 1, 2, 3, 542B, 588, 590B and Proto I were tested with both

ball and tracer amuunition. All other barrels were tested with ball

ammunition only. No definite conclusions can be made concerning the

effects of tracer ammunition upon barrel erosion life since this test

was not designed to evaluate the differences in erosion rates between

tracer and ball ammunition. Ruptured projectile jackets were encountered

with the tracer ammunition. Figure 6, Appendix C, show that the jackets

are stripped while the projectiles are in flight.

The barrel designated EXO01 was designed and fabricated by Manu-

facturer X. This barrel was fabricated in two parts, an 18-inch forward

section which was made from Cr-Mo-V steel and a rear section that included

the chamber which was made entirely from stellite. This barrel was re-

jected after 990 rounds of the schedule were fired. A past history of

2000 rounds claimed by the manufacturer was not verified up to the time

of the completion of the tests.

All of the barrel rejections were based upon the projectile insta-

bility criterion. None of the barrels exceeded the criterion of a loss

of 200 feet per second or more in projectile velocity. The average

firing rate used throughout this test was 200 shots per minute.

RECGOOMBDATIONS

It is recommended that barrel of the Springfield Armory prototype

design be considered to replace present monobloc, unlined, unplated

barrel used in the 5.56mm SAWS candidate machine guns.

-2-

Ad

REPORTSA-TR1-7025

INTRODUCTION

In December 1964, a comprehensive study of all rifles and machine

guns either being used by or oe ng submitted to the field forces was

initiated by the U.S. Army Materiel Co-mand. This study included a

class of weapons in which the 5.56mm cartridge is used. Springfield

Armory's assignment in this effort was to test existing barrels and,

if necessary, to develop a satisfactory barrel for military use.

A preliminary study on 5.56mm barrels showed that it would be

extremely unlikely that a 4150 steel monobloc untreated barrel could

withstand high temperatures and erosive effects of the propellant gases

in repeated firing of a machine gun in the field. Sample calculations

showing heat and stress in the barrel components during firing are shown

in Appendix A. From these preliminary calculations, materials were

selected and physical dimensions were determined for the retainer, the

tube, and the liner for a 3-piece barrel. Drawings for the barrel were

then prepared. Scaled-down prints of the detail and assembly drawings

are included in Appendix D. Gages and fixtures needed for fabricating

and inspecting components, assembling the liner, plating the bore, and

for proof-firing were designed and built at Springfield Armory.

MATERIEL

Ammunition. 5.56mm Cartridge - Livks~d Metallic Belt, 4 Ball, M153,

1 Tracer, M196

Ammunition Lot. Ball Ra 5122; Tracer RA 5025

Test Receiver Assemblies. 5.56mm, M.G., Coda X, with Trigger Assemblies,Serial Nos. 000565, 000578, 000588, 001169,001209, 001213, 002271

-3-

REPORT

SA-TRI-7025

MATERIEL - Continued

Test Trinaer Assemblies. Two, with Solenoid-Operated Triggers

Test Barrels. Eleven barrels were procured from Manufacturer X.

Eight of these barrels - Nos. 1, 2, 3, 542B, 5880, 5908, 810, and 811

were of the standard design and were made from 4150 resulphurised steel.

Two barrels - Nos. NI and N2 - were made from 4150 resulphurised steel

with nitrided bores. Each of these barrels was equipped vith a 3-positionr

gas port adjustment valve. Barrel EX001 was made with a 2-piece con-

struction, stellite breech threaded to an 18-inch Cr-Mo-V steel forward

section. Barrels Proto I and Proto 2 were of the Springfield Armory

3-piece design with Cr-Mo-V steel tube, 6-inch stellite liner, and

Cr-Mo-V steel retainer. The bores of these barrels, Proto 1 and Proto 2,

were chromium-plated.

Chronograph. Electronics Counters Inc., Model 453, with Lumillne Screens

PROCEDURE

Designo After a preliminary study of the potential firing schedules for

5.56=n machine guns was made, a basic design was selected. The configura-

tion of the design and the materials used in this design provided the

greatest resistance to the high temperature and erosive effects of the

propellant gases. The selected design ws a 3-piece barrel which con-

sisted of a 6-inch stellits liner, shrink-fitted into a chrome-moly-vanadiua

tube and retained in position by means of a chrome-soly-vanadium retainer.

The retainer is threaded to the tube and is torqued in place. To obtain

better wear and greater corrosive resistance, it was necessary to chramium-

plate the bore of th4 tube to a thickness of .0005 to .0015 inch.

-4-

REPORT

SA-TRi -7025

PROCEDURE - Continued

The design procedure vas as follows: The physical dimensions of

the retainer, the tube, and the liner were determined. The design

c6iteria used in the determination of these dimensions were based upon

the pressure and thermal stresses of the barrel components during

firing. These procedures with sample calculations are included in

Appendix A. These procedures are given in greater detail in Snainerin&

Design Handbook: Gun Tubes, AMCP 706-252. Drawings were prepared on

the basis of the calculations. A compleLe set of drawings - detail,

subassembly and assembly - are included in Appendix D.

Develo¶,_ent of Fabrication Technigues.

Fabrication processes and plating techniques for stellite-lined

and chromium-plated machine gun barrels were previously developed at

Springfield Armory and were used in the manufacture of the 7.62mm M73,

the 7.62as M60, and the caliber .50 M485 machine gun barrels. The basic

compoaaents for a barrel of the Springfield Armory design are the tube,

the retainer, and the liner. The components for the 5.56em barrel were

machined without difficulty even though the bore sie was consider4bly

smaller than that of the production 7.62mm barrels.

The tube and the retainer were made from Craio-V steel and the

liner 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-lating

of a barrel bore of the 5.*5m caliber had been previously demonstratedo

-5-o

REPORT

SA-TRi -7025

PROCEDURE - Continued

Develotment of Fabrication Techniques.

a routine process had not yet been developed. Some experimunation in

anode-sizing, anode holder design, and electrolyte-pumping rates was

required to establish the proper plating techniques for plating the

5.56mm barrel tubes.

Liner Assembly.

Since the assembly of the liner to the tube requires a shrink-fit

condition, the tube must be heated prior to assembly of the liner. In

the present 7.62mm production methods, a special machine is used to force

the tube over the liner and maintain rifling alignment of the liner during

the assembly operation. Minor adjustments of the machine were required

to assemble the 5.56mm liners and tubes since this machine was designed

primarily for assemoly of 7.62mm liners and tubes. A sectioned view of the

liner and the tube is shown in Figure 2, Appendix C. It should be noted that

the rifling in the liner and the tube in this photograph is not in alignment.

After the liner and the tube were assembled, a high pressure test

cartridge was fired through the liner-tube assembly to set the liner. A

firing fixture that would accept the liner-tube assembly was used to fire

the high pressure test cartridge. After the retainer was assembled to

the tube-liner assembly, a second high pressure test cartridge was fired

in the assemlby.

A complete set of gages was designed and fabricated by the Inspection

Engineering Branch, Springfield Armory. These gages were used to measure

-6-

REPORTSA-TR- -7025

PROCEDURE - Continued

the chamber, headspace, and rifling alignment. The following Springfield

Armory drawing num.bers were assigned to these gages:

Drawing Number Gage Title

C-11703121 Chamber Gaging Ring

C-11703122 Taper Plug (Min. Rear Body Diameter)

C-11703123 Taper Plug (Max. Rear Body Diameter)

C-11703124 Taper Plug (Min. Front Body Diameter)

C-11703125 Taper Plug (Max. Front Body Diameter)

C-11703126 Taper Plug (Min. Cartridge Neck Diameter)

C-11703127 Taper Plug (Max Cartridge Neck Diameter, Front)

C-11703128 Taper Plug (Max Cartridge Neck Diameter, Rear)

C-11703129 Taper Plug (Depth of Bullet Seat)

C-11703130 Special Plug (Min. Bullet Seat Diameter)

C-11703131 Special Plug (Max. Bullet Seat Diameter)

C-11703132 Special Plug (Depth of Second Shoulder)

D-11703201 Headspace

D-11703202 Chamber Indicator and Setting Check (Depth ofFirst Shoulder)

F-11703341 Liner Alignment with Tube

The bore and groove diameters were measured by use of the appropriate

air spindles and associated air column accouterments.

"-7-

REPORTSA-TRI-7025

PROCEDURE - Continued

Test.

In the test procedure established for the 5.56= machine gun barrels,

each barrel was subjected to a test schedule consisting of a series of

3000-shot complements at the end of which the bore and groove diameters

of the barrel were gaged and a check was made against the two rejection

criteria. One of the barrel rejection criterion was a 200 foot per second

loss in projectile instrumental velocity. Projectile instrumental veloc-

ities were obtained by use of two Lumiline screens and a chronograph.

The Lumiline screens were located 15 feet and 35 feet, respectively, from

the muzzle of the gun. The recorded instrumental velocities are based

upon the location of the Lumiline screens and represent a distance of

25 feet from the muzzle of the gun.

A second barrel rejection criterion was based upon projectile

instability - 20 per cent of the projectiles fired exceed 15 degrees yaw

when striking a paper target located 100 meters from the muzsle of the

gun. Target hits were monitored by the continuously traversing target

which is driven by an electrically powered roll.

The barrel test schedule was fired at an average rate of 200 shots

per minute in bursts of 9 shots. A test complement of 3000 shots is

obtained when the 200 shots per minute test schedule is maintained for

15 minutes.

Because of the excessive number of gun malfunctions occurbing during

the initial phases of the test, the original 3000-shot test complement

was reduced to a 600-shot test complement.

"-8-

REPORTSA-TR1-7025

PROCEDURE - Continued

Test..

The ammunition supplied for this test was the standard 5.56mm M193

ball and M196 tracer cartridges. This ammunition was shipped to Spring-

field Armory, linked in belts of 150 rounds each and arranged in a sequence

of four ball cartridges followed by a tracer cartridge. During the early

stages of the test, a revised link was substituted to correct the feed

and belt separating problems which occurred during burst firing.

Use of the tracer cartridge was discontinued in the later stages

of the test when it was discovered that the tracer projectiles were

rupturing before striking the target. The ammunition types fired in the

test are listed in Tabulated Data, Appendix B.

RESULTS AND DISCUSSION

The machine gun receiver assemblies used throughout this test were

from a developmental weapon and the rate of malfunctioning was abnormally

high for a weapon of this type. Since one of the primary objectives of

this test was to fire as many projectiles through each barrel as possible,

expedient action was taken to maintain the firing capabilities of the

machine guns. This expedient action required, in many instances, that

repair and replacement of parts be made at the expense of cannibalising

other receiver assemblies.

Even though the number and the nature of the gun malfunctions were

recorded in the test data, this information was not provided in this

report since the objective of this report is principally a barrel study.

"-9-

REPORT

SA-TRi-7025

RESULTS AND DISCUSSION - Continued

The test was initiated with standard barrel No. 1. A total of

514 rounds was fired through this barrel when gun failure required

discontinuation of the test. Since this barrel-gun combination could not

be made operable within the time allotted by the test schedule, this

barrel was removed from the test and not rejected on the basis of the

established rejection criteria.

Barrels 2 and 3 were of the standard design with untreated bores.

These barrels were fired a total of 2,509 and 5,088 rounds, respectively,

before rejection. Rejection was based upon the projectile stability

criterion.

Barrel 542B also a standard barrel with untreated bore was removed

from the tests after 1755 rounds were fired. This barrel was withdrawn

because of a damaged barrel extension. A malfunction that resulted in

a cook-off damaged the gun beyond repair.

Barrels 588 and 590B were fired a total of 7,116 and 4,209 rounds,

respectively, prior to rejection which was based upon the projectile

stability criterion. These barrels were also of the standard type with

untreated bores.

Barrels SIO and Sll were of the standard design with untreated bores.

These barrels were rejected after 7,842 and 12,476 rounds, respectively,

were fired. The cartridge type used to test these barrels was restricted

to the M193 ball ammunition since possible rupture of the tracer projectiles

could affect the rejection criterion

-10-

REPORT

SA-TRI-7025

RESUtLTS AND DISCUSSION - Continued

The barrels designated N1 and N2 had bores which were nitrided by

a process devised by Manufacturer X. These barrels were injected into

the test after the test had started and were fired 29,874 and 26,774

rounds prior to rejection. These barrels were rejected on the basis

of the projertile stability criterion. The barrels had velocity losses

of 30 and 75 feet per second, respectively.

The barrel idenLified by No. EXOOI was designed and fabricated by

Manufacturer X. This barrel was of the 2-piece construction design with

an 18-inch forward section made entirely of Cr-Mo-V steel; the rear

section which included the chamber was made of stellite. This barrel was

rejected after 990 rounds of ball ammunition had been fired. The manu-

facturer claimed a previous history of 2000 rounds. No information was

given by the manufacturer concerning the rate of fire, the firing schedule,

or the type of ammunition fired.

Barrels Proto I And Proto 2 were designed and fabricated by Springfield

Armory. Th~e barrelu were of the 3-piece construction design. The three

pieces, or components, are the retainer, the stellite liner, end the tube.

The tube has a chromium-plated bore. Drawings of these components are

Included in Appendix D. These barrels were rejected after 33,433 and 43,994

rounds, respectively, were fired. Velocity losses of 92 and 107 feet per

second were recorded for these barrels. Rejection of these barrels was

based on projectile Instability.

-11-

REPORTSA-TR• -7025

RESULTS AND DISCUSSION - Continued

Even though the machine guns used as test vehicles for the barrel

erosion tests had an excessive number of malfunctions, test results

revealed that the stell ite-lined and chromium-plated barrels exhibited

superior erosion resistance. It was also evident that the barrels with

nitrided bores showed sufficient improvement over the standard barrels

with untreated bores to be considered also as a replacement for the

standard barrels with untreated bores.

A study of the economics of fabrication for the various types of

barrels would be required to provide cost effectiveness data for the

various types of barrels. This study should include the various aspects

of logistics occurring in field maintenance.

-12-

REPORTAPPENDICES SA-TRP-7025

A - Calculations

B - Tabulated Data

C - Photographs

D - Drawings

E - Distribution

-13ft

REPORTSA-TR107025 APPIX A

CALCULATIONS

144-

REPORTAPPENDIX A SA-TRI-7025

DEVELOPMENT OF A STELLITE-LINED, CHRIKIUK-PLATED BARREL FOR THE5.56MM MACHINE GUN

Shrink Fit Stresses in Liner and RPTAkNER

Shrink Fit Pressure between tubeand liner

PSI : Shrink fit pressure between tube and linerri : Radius of Bore : 220 .x10"

rI : Outside Radius of Liner - .407 • .2035"

r2 : Outside Radius of Tube : .716 ; .3582

1 I interference between tube and liner = .0012"

EB : Modulus for steel 2 30x 106 psi

EL Modulus for Stellite a 35x106 psi

Uj Poisson's Ratio of Steel " 0.3

UL - Poisson's Ratio of Stellite " 0.3

Ps 91 II

.2 2 L

ri r .o92 + ..... . . .. .. 1. .. . ... . .

ExO 2 r 2-E L.2n- L

ri

.235 1 .3582 + .*Q +1 .2035 + .110

3582035 2035( 11-

- 49,660 psi

-15-

REPORTSA-TR1-7025 APPENDIX A

Shrink Fit Pressure between tube and retainer

P9 2 : Shrink fit pressure between tube and retainer

r0 : Outside radius of retainers = 1 = .5125"

12 : Interference between tube and retainer = .0012"

E.... " . _r 2 2Ps . E 12 (r22 0r2 r 2-.

2 r 23 (ro 2 - r12)

:30x0 6 (.0012) (.35-82 -. 2 ) (_5---2 - 2 )

2 (.358) 3 (.3ý2 _..110-)

Ps2 18272 psi

Shrink fit stressat inner surface of liner

St.,- Stress resulting from P.1StsI=-Pl 2 r12

2 2

r - ri

:-49,660 ( 2) 7MT~2

: -140,319 psi

St. : Stress resulting from Ps2

ts 2 s2 2 r2r22 ri

:-14,27 2 (2) .35-82

- -40,332 psi

-16 -

REPORTAPPENDIX A SA-TR1-7025

Shrink fit stress at outer surface of liner

StaI : Stress resulting from Psl

S taI :.Pal r12± r,2

12 2

"" 49,)t60 (1.8256)

- -90,659 psi

S t82 Stress resulting from P.2ts2 2

Sis2 - p r 2 r 2 2Ss 1 2 (r +ri 2

2 -

s ts2 1827 128164 .053512251.04141 128164-.02

: -26,072 psi

Shrink fit stress at inner surface of the tube

SisI: Stress resulting from P8s

S tl P.1 (r2 2 + r1 2 )

9 2 _r 12

: 49,660 (1.9547)

: 97,070 psi

St2 : Stress resulting from Ps2.. p r 2 2

S t#2 ".2 ___2 •r + r 12)

r12 (r 22 ri2

1 2 1 A

" -26,072 psi

-17-

I

REPORTSA-TRi-7025 APPENDIX A

Shrink fit stress at outer suriare of tube

s Stre3s resulting froim Ps2

S 2 r

r 1

49P60 (2) (.041412) S=47,411 psi.086752

S, Stress resulting from P.2

: P52 (S 2 2

r 2 r 22

ts2 14272 ( .128164 +.0121 ) -22,082 psi.116064

Shrink fit stress at inner surface of retainer

StsI: Stress iesulting from Psi

S SS - Stress resulting from Ps2

tS2

SP ( r0 2 + 2

s2 2

2 - r 2o 2

: 49,660 (.262656 + .128164 ) : 49660 (.390820).134492 .134492

= 144,307 psi

-18-

REPORT

APPENDIX A SA-TRI-7025

Shrink fit outer surface of retainer

S ta - Stress resulting from P.1

Sts1= 0

S t -2 Stress resulting from P.2ts2 2

5ts2 : P8 2 2 r2

S02 - r 22

49,660 (2) ( .128164 ) 94,642 psi

.134492

Gas Pressure Stress at inner surface of liner

Stp - Stress resulting from gas pressure

Pd Propellant gas pressure 5h,000 psi

SiP : Pd (to2 + r. )

2 2r - ro

56P0O (.2b2656 +•0l2l).250556

: 61,410 psi

Gas Pressure Stress outer surface of liner

" P ri2 r 2

" d _ (r._r2

02- ri2

S : 56POo ( 0.1ii ) (.262656 +ý*Ig§164 Itp .041412 .250556

- 25,521 psi

-19-

REPORTSA-TR1-7025 APPENDIX A

Gas Pressure stress inner surface of tube

Stp : 25,521 psi

Gas Pressure stress at outer surface of tube

j P r 2 ro2 2

2 0 ri2

: 56OO (.0121 ) (1.5598).128164

8,246 psi

Gas Pressure Stress at inner surface of retainer

Sip "8,246 psi

Gas pressure stress at outer surface of retainer

Stp P5d 2 ri2

2 2I[ "r

0

54000 (2) ( .0121 )

.250556

: 5,408 psi

Combined stress at inner surface of liner

Scil.: Combined stress at inner surface

Sts1 : Tangential Stress due to Ps5: -140,319 psi (see page 16 )

Sis2 Tangential Stress due to Ps2: '40,352 psi (see page 16 )

Stp Tangential Stress due to Gas Pressure : 61,410 psi (see pasg 19)

-20-

REPORTAPPENDIX A SA-TRI-7025

Sc1i a St1s + Sts 2 + Stp

z - 140,319 - 40,352 + 61,410

$ci1, 5 -119,261 psi

Combined Stress of outer surface of liner

ScoL a combined stress

Ste Tangential Stress due to Pal : -90,659 psi (see pase 17)

Sts2 : Tangential stress due to P#2 : -26,072 psi (see page 17)

Stp 2 Tangential Stress due to Gas Pressure 8 25,521 psi (see page 19)

ScoL : St5 , + Sts2 +Stp

= -90,659 - 26072 + 25,521

- -91,210 psi

Combined stress of inner surface of tube

Scit : combined stress at inner surface

S tsl : Tangential stress due to Psl 3 97,070 psi (see page 17 )

Ste : Tangential stress due to Ps2 :- 26,072 psi (see page 17 )

Sp : Tangential stress due to gas pressure * 25,521 psi (see page 19)

8cit tSte I St42 + Stp

8 Cit: 97,070 - 26072 + 25,521

= 96,519 psi

-21 -

REPORTSA-TR1-7025 APPENDIS A

Combined Stress at outer surface of tube

Sc combined stress at outer surface

: Tan stress due to Psi': 47,411 psi (see page 18)

Sts 2: Tan stress due to Ps2 -22,082 psi (see page 18)

S : Tan stress due to gas pressure : 8,246 psi (see page 20)tp9

+ Sis +SS cot :Sts 1t tp

Scot 47,411 - 22*82 + 8,246

33,575 psi

Combined stress at inner surface of retainer

Sci1 : combined stress at inner surface

St : Tan stress due to (see page 19 )

S : Tan stress due to Ps2 : 144,307 psi (see page 18 )

S : Tan stress due to Gas pressure : 8,246 psi (see page 20)tp

Scic S ts- +St82 + Si p

"0 + 144,307 + 8,246

: 152.553 psi

-22-

REPORTAPPENDIX A SA-TRI-7025

Combined stress at ouLOT surface of retainer

Scoca combined stress at outer surface

Sto, a Tan strehs due to P.1 : 0 (see page 19 )

StS2: Tan stress due to P 2 94,642 psi (see page 19)

Stp : Tan stress due to gas pressure x 5,408 psi (see page 20)

Scoc S ts1 + S t 2 + StP

* 0 + 94,642 + 5,408

: 100,050 psi

Maximum stress of assembly occurs at inner surface of retainer and has a

value of 152,553 psi.

-23-

REPORTSA-TR1-7025 APPENDIX B

TABULATED DATA

-24-

cc ~ 0:

0 0.

Zi i La J i

oi

4 z

to 0 0

it in( d-~j <0 a) IT in 0

w ~ 6) inn P

(ID _0 _ 1 r - -in -

-r c N

010I1 0 0 0 0 00 00cc.0 00 0 0J U Al N J 00 0 0

X U)

CLb

-1 Li<

- x- -- -1

-iTz z: zz z zz zz z z w"ao

_ji

-j0 w wLaw w Vl) La w

< I.J WI P.uJI o

0 o o 0

II U 0 0 0--NO

REPORTSA-TR1-7025 APPENDIX C

PHOTOGRAPHS

Fiture Caption

1 5.56m Lined Machine Gun BarrelSpringfield Armory Design

2 5.56m Tracer ProjectilesFired from Machine Gun during Erosion Test

3 Tooling Setup Barrel:Tube and Liner Rifling Alignment for5.56mm Lined Machine Gun Barrel

A 5.56an Machine Gun Firing RA5025 Tracer Amunition:

Upper Left. L2 Barrel - Ball Am. 16 In. from MuzzleUpper Right. L2 Barrel - Tracer Am. 16 In. from MuzzleLower Left. L2 Barrel - Tracer Am. lo in. from MuzzleLower Right. New Barrel - Tracer Am. 16 In. from Muzzle

5 5.56m Machine Gun Firing RA5025 Tracer Amunition:

Upper Left. L2 Barrel - Tracer Am. 11 In. from MuzzleUpper Right. LZ Barrel - Tracer Am. 16 In. from MuzzleLower Left. L2 Barrel (Cold) - Tracer Am. 16 In. from MuzzleLower Right. L2 Barrel (Hot) - Tracer Am. 16 In. from Muzzle

6 5.56=m Machine Gun Firing RA5025 Tracer Amunition:

Left. L2 Barrel - Tracer Am. 16 In. from MuzzleRight. L2 Barrel - Tracer Am. 16 In. from Muzzle

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DRAWINGS

WWI Tile

SAF51210 Tube, Barrel

SAD51211 Liner, Tube

SAD51212 Retainer, Liner

SAF51213 Barrel Tube Subassembly

SAD51214 Barrel, Tube Assembly

SAD51215 Barrel Subassembly

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UNU60LFL~yWSecurity Classification

DOCUMENT CONTROL DATA - R&D(Security classification *If title, body of abstract and indoxinjf annotation must be antered when the overall report Is csolaeeffe)

I.- ORIGINATIN 0 ACTIVITY (Corprate author) I*, AftPORY SE9CURI TY C LASSIFICAITION

UnclassifiLedSpringfieold Armory, Springfield, Mass. 01101 2 b, GROuP

NAo3. REPORT TITLE

DEVELOMWENT OF A STELLITE-LINED, CHRQ(4IUM-PIATED BARREL F0R5,56MM MACHINE GUN

C. DESCRIPTIVE NOTES (Type of report and inclusilve date#)

Technical Report1. AUTHOR(S) (Lost Mamo, fiIret nameo, Initial)

Jarrett, W. J. - Registered Professional Engineer, Comonwealth of MassachusettsReais traton N.j.19Z~76

6. RE PORTY DATE Is. TOTA LNO.OF PAGES 1b. ý40. Oir mrIs

30 June 1967 45None.@a. CONTRACT OR GRANT No. N.A. 08. ORIGINATOR'S REPORT NUM89IR(S)

66 PROJECT No. 1W523801A30408 SA-TRI -7025

c, AMO4S CODE 5523.11.45808,08.01 tb o Top rJ PORT NO(S) (Any othemnRuntbera 1hat May be aea01a

10. AVA TYLNTTO OTICES Qu ed reque as may obtain cope of t repotft Def aDoc nt ion or, Maerv tat& a. Al ata Virg 22 14.

ramypur so pies fthis ropo frm ode atou roaJl

11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY

NoneU.S. Army Materiel Command

ill. ANTRACT

The procedure as developed by Springfield Armory for design andfabrication of a stellite-lined, chromium-plated barrel for the5,56mm machine Sun 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 Inerosion resistance. One of the stellite-lined barrels was fired43,994 rounds prior to rejection. A maxim.m of I3,4-%6 4warfired from one of the standard barrels prior to rejections, Thetwo other types of barrels -a standard barrel with a nitridedbore and a barrel of two-piece construction -were fired 29,874and 900 rounds, respectively, before rejection. The two-piecebarrel has an 16-inch forward section mae" from Cr-(o-V steeland the rear section, including 4hd chamber, is made entirelyfrom stellite. All barrels were rejected en the basis of theprojectile instability criterion - 15 degrees yaw of 20 per centof the projectiles fired, All bc~rrel3 Were fired at an ameragerate of U0 shots per minute.

DD I JAN 44 1473.. ___ ___ ___ __

swurty CassficaloI

UNCLASsiFIED __

Security Classification LN IK

KEY WORDS LINKALNK_ LINK C____________________________ R OLE WT S.OLE WT RtOLE Wr

1. Barrels, Machine Gun, 5,56mm*.. *, ), .

2e Stullite-lined riachins Gun Barrels, 5.56o

3* Eros ion in SmallI Arms Machin* Guns

4. Buall Atm Weapon Systems (SAWS)

INS aICTIONS -I

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miiaydprmn ~~iaod&ha rjc ubr C;o f)~* * .subproject number, SyStelftnfo~mbers, task riumhar,. btc. 'There Is no0 limitation oni 4he lemroltha th~ab4tract, How-Sa. RIGKATR'SREPRT aIUWER(6). 'nte th oft~ over, the su~psted- length is from ýý -uto 225 rweds.

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_____________________________________________optional.

UNCLASW?3DSecurity Classification