NAW RESEARCH SVCTjtISCIENCE DIVISION -REFERENCE DEPARM~N1LIBRtARy OF CONGRZSS

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REPORT HO 896

ROTATIIG BAD STUDY ,4 2nd Partial Report

TEST OF 3/70 AA PROJECTILES WITH

ARMCO IROII ROTATIIlG BANDS

I st Partial TaskReport Assignment NPG-Re3b-225-1-52

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'NPG REPORT NO. 896

U. S, NAVAL PROVING GROUN1DDAHLGREN, VIRGINIA

Second Partial Report

on

Rotating Band Study

First Partial Report

on

Test of 3"/70 AA Projectiles with

Armco Iron Rotating Bands

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Project No: NPG-Re3b-225-l-52 Date: NOV 2 9 1951Copy No.:

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No. of Pagcs: 7

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IU IJNCLAS1FRNPG REPORT NO. 896

Test of 311/70 AA Projectiles with Armco Iron Rotating Bands------ - - - - - - - - - - - - -a - -

PART A

SXNOPSIS1

1. 31/70 projectiles of various types, fitted with gilding metalrotating bands, have been observed to exhibit serious band wear;that is, partial or complete obliteration of the engraving of thebands recovered after firing. It was desired to investigate theeffect of replacing the gilding metal with soft iron, in order todetermine the results of using a material with a considerablyincreased melting point, and if this change would produce a bandwhich did not fail, to determine the effect upon gun performance.

2 It is possible to fit a 3"/70 projectile with a soft ironband using precisely the same method of manufacture as for agilding metal or copper band. The hardness of such a band isapproximately the same as that of a gilding metal band.

3. Armco ingot iron bands of the standard 3"/70 Ex 24-2 contour,fired from the 31"/70 gun Type G-3, showed no band wear. Similargilding ietal bands were almost completely worn away. As a con-sequence, the iron bands showed considerably less tendency tofringe.

4. Barrel strain values are little if any higher for iron bandsthan for gilding metal bands,

5. On the basis of a range test in the G-3 gun of twenty pro-jectiles of each type, the iron banded projectiles gave an averageD/R of .45' and the gilding metal banded projectiles gtive 2.20'.

6. Since the major uncertainty about the iron band is its effectupon gun wear, it is recommended that the Bureau of Ordnance takesteps to obtain a sufficient number of iron banded 3"/70 pro-jectiles to perform a life test on at least two barrels. Theseprojectiles should be similar to the Type Ex 24-7, except for bandmaterial.

1 UNCLASSIFWID4

II

NPG REPORT NO. 896

Test of 3"/70 AA Projectiles with Armco Iron Rotating Beands -"~- - - - - - ----------------------- -- ---

TABLE OF CONTENTS

SYNOPSIS, , . . . , . * . , , . . . , . . , . .. . I

TABLE OF CONTENTS . . ....... . ..... 2

AUTHORITY . * a . . . * * . * a , . 0 . . 0 . . . # 0 3

REFERENCES. . . . . . . . . . . . . . . . . . . . . . 3

BACKGROUND. . . , . . . . . . . . . . . . . . . . . 3

DISCUSSION, . . . . . . . . ,° . . . . . .* * * 5

CONCLUSIONS . . . . . . . . . .. . . . . . . . .. . 6

RECOMMENDATIONS... ...... . . . . ... . , 6

APENDIX A - COMPLETE BEFORE AND AFTER FIRINGDATA. . . .. . . , * * , & TABLES 1-II (Incl)

APPENDIX B - TENSILE TEST RESULTSCHEMICAL ANALYSISHARDNESS RE:SULTS . . . . . . . . TABLE I II

APPENDIX C- RANGE DATA. . . ; . . . . .. . TABLE IV

APPENDIX D - BARREL-STRAIN SUREMENTSSTAR GAUGE DATA. . . . . . , , TABLE V 1-2 (Incl)

APPENDIX E - NPG PHOTOGRALPHS AND SKETCHES . . FIGURES 1-16 (Inci)

APPENDIX F - WIRE IMPRESSION HETHOD OF DETERMININGS P I N & .* * * .* * * * .* a 6 , .* 1i ( O n l y )

APPENDIX G- DISTRIBUTION, . • * . * • . • a .. 1 (Only)

mo 2

CONFIDENTIAL NPG REPORT NO. 896

Test of 3"/70 AA Projectiles with Armco Iron Rotating Bands~~~~~~~- - - - -- - -- - ------------------- - -

PART B

INTRODUCTION

1. AUTHORITY:

This program was authorized by reference (a).

2. REFERENCES:

a. BUORD Conf ltr NP9 Re3b>-RS:mt Ser 24422 of 15 August 1951b. NPG Report No. 626 of 18 August 1950co NPG Report No. 750 of 20 March 1951d. NPG Report No. 787 of 2 June 1951ei NPG Report No. 860 of 13 October 1951f. NPG Range Sheets Nos, 130 and 131

3. BACKGROUND:

It has been suspected for some time that the poor accuracyresults obtained with the 3"/70 gun were at least partially to beattributed to the failure of the gilding metal .,otating bands, asmight also be attributed the body engraving of the projectiles andthe spiral wear of the gun. The observed phenomena were describedin references (b), (c), (d), and (e), and reference (b) suggestedthat the band wear (partial or complete obliteration of engraving)might be caused by "loss of copper on the driving edges by abrasion,or by local frictional heating to the point of loss of strength oractual melting". Reference (b) recommended "that a few 3"/70 pro-jectiles be fitted with soft iron bands of contours similar tothose in current use, and fired for recovery to determine whetherthe higher melting point of the iron will produce improvement inthe performance".

CONFIDENTIALSECURITY INFORMATION 3

[CONFIDENTIAL NPG REPORT NO. 896

Test of 3 "/?0 AA Projectiles with Armco Iron Rotating Bands- - - - - - ---------------------- -----

PART C

DETAILS OF TEST

4. PROCEDURE AND RESULTS:

The Proving Ground found that it was possible to apply a softiron band (Armco ingot iron) in exactly the same manner thatcopper or gilding metal bands are applied, that is, by swaging ona ring of the material in a standard banding press. The swagingwas done on a West Tire Setter #2 at a gauge pressure of 900 p.s.i.,on material at room temperature, and the bands were then machinedto finished dimensions. No excessive work hardening was caused bythe process. Chemical analysis and tensile test results for theArmco iron, used, which was in the form of bar stock, as well ascomparative hardness readings for the iron bands and for standard3"/70 gilding metal bands are given in Table III, Appendix (B).It is seen that the iron bands fall within the hardness range ofthe gilding metal bands.

Three 3"/70 projectiles Ex 24-2, furnished to the ProvingGround for experimental work without band or band score, werefitted out with two " Armeo iron bands, diameter 3"09, inaccordance with Figure 14. Pnd were fired for recovery from the3"/70 gun Type G-3 along with three projectiles with gilding metalbands of the same contour and applied in the same manner, for'co-parison. Detailed results are given in Table I, Appendix (A), andtypical photographs of the recovered projectiles are shown InFigures 3 and 4, Appendix (E).

Since the muzzle strain results and the hardness values showednot much difference between iron and gilding metal, it was decidedthat it would probably be safe to fire iron banded projectileswith the standard 3"/70 band contour, Accordingly, six ironbanded projectiles were made up, three with the standard Ex 24-2after band contour, fand three with the same contour modified by arelief groove aft of the forward lip (Figure 15, Appendix (E)), toreduce barrel strain. These were fired for recovery along withthree gilding metal banded Ex 24-2 projectiles, with the forwardband turned down to body diameter, as is necessary for firing inthe G-3 gun. Detailed results are given in Table II, Appendix (A),and photographs of the recovered projectiles are shown in Figures 5through 12, Appendix (E). Barrel strain results -nd star gaugereadings are shown in Table V, Appendix (D).

CONFIDENTIALSECURITY INFORMATION 4

CONFIDENTIAL ...G t A; 896

Test of 3'1/70 AA Projectiles with Armco Iron Rotating Bands~~- - - -n~ -- - - - --- - - - - -- - - - - - - -C

In view of the absence of band wear and fringing of therecovered bands and the favorable barrel strain results a rangingprogram was arranged to determine whether a non-failing bani wouldgive improved range performance in the G-3 gun, which had neverperformed with satisfactory accuracy using gildirg metal bands.Twenty iron banded projectiles (Ex 24-2 contour) and twenty standardEx 24-2 gilding metal banded projectiles, with the front band turneddown, were fired alternately in this program, the detailed resultsof which are given n reference (fM, and a summary in Table IV,Appendix (C). Briefly, the D/R for the iron banded projectilesaveraged .45%, and for the gilding metal banded projectiles 2,20%.The average ranges wore 14098 yards and 14036 yards, respectively.

5. DISCUSSION:

On the basis of the results described, it would appear thatthe only objection to the use of the ingot iron band would be itspossibly deletei-lous effect upon gun life. This should certainlybe investigated, and more information on range results simultane-ously obtained. Furthermore, it would be most interesting todetermine whether a gun fired with non-failing bands would developthe spiral wear observed hitherto in the 3 "/70 guns.

The range results obtained so far are surprisingly good, asregards dispersion, It is not easy to see why there is not agreater range differential between projectiles with the two typesof band. Possibly this is to be attributed to the greater rough-ness of the iron band. The recovery results lend support to thebelief that the band wear observed with gilding metal is caused bylocal frictiohal heating of the band to a temperature near themelting point, with consequent loss of strength, rather than anyeffect of abrasion or gas erosion.

It is planed to conduct firings with iron banded projectilesin other 3"/70 guns with disappearing and with trpored-depth 'rifling. No non-failing band has yet been fired in these guns,and it is conceivable that with such a band, muzzle strains mayrepch undesirably high values, If not, range data will be obtninedfor these guns also,

CONFIDENTIALSECURITY INFORMATION 5

. .. . . . . . . . . ..-- - --- - -2

NPG REPORT NO. 896

Test of 3 "/ 7 0 AA Projectiles with Armco Iron Rotating Bands

PART D ..

CONCLUSIONS

6. a,. It is possible to fit a 3"/70 projectile with a soft ironband using precisely the same method of manufacture as for agilding metal or copper band. The hardness of such a band isapproximately the same as that of a gilding metal band.

b. Armco ingot iron bands of the standard 3/70 Ex 24-2contour, fired from the 3"/70 gun Type G-3, showed no band wear.Similar gilding metal bands were almost completely worn away. Asa consequence, the iron bands showed considerably less tendencyto fringe..

c. Barrel strain values are little if any higher for ironbands than for gilding metal bands.

d. On the basis of a rango tcsz in the G-3 gun of twenty pro-jectiles of each type, the iron bandud projectiles gave an averageD/R of .45% and the gilding metal banded projectiles gave 2.20%

PART E

RE C 0 M NCEIDAT I ON S

7, Since the major uncertainty about the iron b-.nd is its effectupon gun wear, it is recommended that the Burcau of Ordnance takesteps to obtain a sufficient number of iron banded 3/70 pro-jcctilcs to perform a life test on at lerst two barrels. Theseprojectiles should be similar to the Type Ex 24-7, except forband matorial.

6 .i NC ,.S, F i ED

[NiG REPORT NO. 896

Test of 3"/70 AA Projectiles with Armco Iron Rotating Bands

The tests upon which this report is based were conducted by:R& D4 CROM-WELL, Plate Puze Battery Officer

Terminal Ballistics DepartmentD. C, CAIN, Head of Ammunition Division Research Branch

Armamefit DepartmentR. B. BUTLER, Head, Design Branch

Terminal Ballistics Department

This report was prepared by:R. T1. LYDDANE, Director of Research,

Terminal Ballistics DepartmentR. B. BUTLER, Head, Design Branch

Terminal Ballistics Department

This report was reviewed by:R. H. LYDDANE, Director of Research,

Terminal Bllistics DepartmontW. B. ROB.92RSON, Lieutenant Commander

Terminal Ballistics Batteries OfficerTerminal Ballistics Department

R. T. RUBLE, Lieutenant CommanderTerminal B:illistics OfficerTrmina l Ballistics Department

C. C. BRAMBLE, Director of Research, Ordnrnce Group

APPROVED: IRVING T. DUKERe.r Admiral, TJSNCor-andcr, Naval Proving Ground

C. T. MAUROCaptain, USNOrdnance OfficerBy direction

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CONFIDENTIAL NPG REPORT NO. 896

Test of 31/70 AA Projectiles with Armco Iron Rotating Bands

TABLE III

Tensile Test Results - Armco Iron Used in Test

Y. S. T.S.('04 s, i ~ (p.Si E14 %-R.)A

20,000 38,800 49.5 76.2

Chemical Analysis-- Armco Iron Used in Test

C Mn P S Cu Al

.025 .0A 0ll .024 .10 .006

Hardness Results

Rockwell 15-T Scale

Before FirinM After Firln&Grooves Ridges

Gilding Metal Bands 81(79-83) 79.9(74-83) 80.4(79-84)

Armco Iron Bands 83(82-84) 83.5(80-86) 82.9(80-85)

Hardnesses of Gilding Metal Commonly Used for3"/70" Rotating Bands

Manufacturer Hardaess-Rckel;

Kelsoy Hayes 84.1

Bethlehem 81.5

Lnnsdowno Co, 83,4 & 82.6

Midvalo 80.8

Motor Wheel 85.3

CONFIDENTIALSECURITY INFORMATION APPENDIX B

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NP9-45527 9 March 1951 CONFIDENTIALPhotograph of Y"/70 AA Projectiles Type Ex 24 Mod 2 with, two1"1 bands, before firing.Figure 1

NP9-45528 20 April 1951 CONFIDENTTALPhotograph of Y"/70 AA Projectile Type Ex 24 Mod 2, modified,with Arinco iron band before firing.

Figure 2

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NP9-45529 9 March 1951 CONFIDENTIALPhotograph of recovered 3"/70 AA Projectile Type Ex 24 Mod 2

with two 1" Armco iron bands.Figure 3

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NP9-45 532 20 April 1951 CON~FIDENTIALThree v~ews (1200 apart) of recovered 3"/70 AA Projectile

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UP9-45556 20 April 1951 CONFIDENTIALThree views (1200 apart) of recovered 3"/?0 AA Projectile

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NP9-45557 20 April 1951 CONFIDENTIALThree view= 1,'0 a part) of recovered )"/70 AA Projectile

Type Ex 24 Mod 2 with gilding-metal band. Projectile No. 603.Figure 13

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CONFIDENItAL-

;ur~E /~

N-G REORT NO. 896

Test of 3"/70 AA Projectiles with Armco Iron Rotating Bards

Wire ImPression Method of Dctermining- Soil%

Two screens are set up 41.5 apart, each screen con_iztng ofa metal frame with wood inserts, holding an array of parallel 1Cequidistant vertical copper wires. The spacing of the wires is1/2"1 for the first screen and 3/4" for the second. The projectile C)is fitted with a flat-nosed dummy nose plug or the equivalent, so -that after passing through the screens it bears two sets ofimpressions of the wires, The angle between the two sets of -

impressions is measured and from this measurement the rifling ofthe gun, the muzzle velocity, and the velocity at the spin screens,--is computed the percentage of nominal spin. It is assumed thatover the short distances involved the spin retardation is negli-gible.

F

/

PG REPORT NO. 896

Test of 3 "/ 7 0 AA Projectiles with Armco Iron Rotating Bands

DISTRIBUTION

Bureau of Ordnance

Ad3 1 5Re5 1 (4Re3 1

Re3b 1

Chief of OrdnanceDepartment of the ArmyAttn:. ORDTX-AR 2

Commanding GeneralAberdeen Proving OroundAberdeen, MarylandAttn: Techlnical Information Section

Development and Proof Services 1

Commanding OfficerFrankford Arer alPhiladelphia, Pennsylvania 1

Navy Research SoctiorLibrary of CoigressWashington 25, D. C. Gc(Via BUORD Re5) 2

Local:OTE-l 1OT-I 1OT 1OML 1File I

UNCLASSIFIED

As;M '-M M - PENDIX G

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