Bore Erosion and Accuracy of M16A1 Rifle

189 Pages·2013·4.52 MB·English

- -),I R-TR-77-055
0BORE EROSION AND ACCURACY
OVM16A1 RIFLE
DRD.' RAO YALAMANCHILI
Reproduced From FBUR 97
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Best Available Copy
v ~AR 31191
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3'. GENERAL THOMAS J. RODMAN LABORATORY
ROCK ISLAND ARSENAL
ISLAND, ILLINOIS 61201
- *ROCK
4 70-
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*The findings of this report are not to be construed as an Official
Department of the Arny position unless so designated by otbe,' authorized
documents.
StCURITY CLASSIVICATIsO Of THIS PAGE (1WhooD ole EKleod
REPORT DOCUMENTATION PAGE BOREA COSTRUCTIONSOR
3ovT ACCESSION No. 3. ItECiPiEH SIDE
u-
i-R-777Y
4* "ITLE~ans""Itlo) S. TYPE OJUEPO 'R-9PERI1OC COVERED]
.jRLR~O -ADACCUR0AFC1Y41 661 BIFLE, O Final*FeCf ilJun7
Rao alamanchi ii
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMEN. RJET TAI
Research Directorate, SARRI-RIR AE WOKUIT NUMBERS
GEN Thomas J1.R odman Laboratory
Rock Island Arsenal, Rock Island, IL 61201 3210. 16.0131
I.CX"0Lg ~a""
N fhDDRESS
GEN Thomas J. Rodman Laboratory, SARRI-RLRNUBROruy
Rock Island, IL 6120117
M.MONITORING AGENCY NAME & AOORESS(II diti.onat heom Counfrolitd Office) 15. SECURITY CLASS. (of this see~f
UNCLASSIFIED
ISa.OCLASSOIFICATIONIOOWNGRAOING
III. DISTRIBUTION STATEMENT (of hi AbRoped)
Approved for public release, distribution unlimited.
IT. DISTRIBUTION STATEMENT (ofmth elr obstecterodmto Block 2.it different frdoi Roefd)
III. SUPPLEMENTARY NOTES
IS. KEY WORDS, Continue an reverse slde U noccosem a"~I dentify 6F weeck number)
M16Al Rifles Aimmunition
Gore Erosion Gages Firing Rates
Accuracy Spread on Target
*ABSTRACT (Continue an reverse side Of1 90coset sod Identify by block finibm)
nanalysis was conducted on the performance of M1l6Al rifles made by three
manufacturers with the use of two kinds of ammunition and three rates of fire.
-Th.ydata Include extreme spread and bore erosion gage measurements, each as aI
functi on of the number of rounds fired. Consistency Is lacking In the experi-
mental data, even though Identical tests were performed. Probably,-thrandom
vibrations of the gun barrel or o er unknown phenomena may be the reason for
Inconsistency of spread data. inossec ithpeetration eo sio
DO , .I?,1473 UNCLASSIFIED
UNCItAS~irirn
SECURITY CLASSIFICATION OF THIS PAGE(Vka, Date EistonDO
-ages may be due to fouling deposits on the bore surface and to lack of properly
des ic ned tools for unique measurements. Large variations. occur In the usefulI
lfofthe barrels due to variations In manufacturing., ammunition. and firing
rate. The typical rate of erosion is about one-thousandth of an Inch per
thousand rounds of fire. Gage Number 6 may be used to measure barrel erosion
and ultimately to Indicate when to discard the barrel. ¶htAcrosion Increases
and *#oV"%eful life of the weapon decreases with Increase in rate of tire. The
useful iffe of the weapon may be approximated as Inversely proportional to the
two-third power of the firing rate.
A
UNCLASSIFIED
________________SECURITY CLASSIFICATION OF THIS PAGE(When Dole Enter**)
CON TS
Page
i
DD Form 1473
Table of Contents iii
I. Introduction
it. Identical Tests 3
6
III. Gage Penetration
6
IV. Bore Profiles
7
V. Gage Analysis
10
VI. Recoumendationl
173
1References
Si
Distribution
ii
iii
I. IflW.'TIO
M16a. rifles are mde by three manufacturers. In addition to the
variations of the different manufacturers, two kinds of maindtion and
three firing rates are utilized. It is possible to consider a consistency
test for standard hamunition, 3193 ball propellant. Thus,, 2 veapons are
involved in this cperinentU. investigation. The weapon metifictis
are hohn In Table I.
The e~orimantal data are tabulated in Reference 1. Tbes. data include
mean radius and extreme spread of hits on the targets, eA nine different
gag. penetratio in the barrel bore near the origin of rifling as fuctions
of number of romdA fired. Since mean radius is considered by mall ama
specialists ma an unimportant factor in barrel selection., no utilization In
nede of the man rdius data in this study.
It is the objective of this task to recommend a gage and criteria
(how much penetration or erosion into the bore) to condemn a barrel, baaed
on the exdwting data of extreme spread and various gage penetrations ma
reported in Reference 1.
Since the extreme spread is an indication of the accurza of a veapon,
the spread data as reported ii Reference 1 is shown in Figures 1 thru 27.
The variable parameter consista of Targets #1s #2, #3 and a mean of all these
---t-hree targets. lhe extreme spread of each target is based on a group of 10
rounds. The quality of data is poor. Since there are large variations from
one target to another and the data varies in a mradm maner, it does raise
soe questions; such as, can the mean of extreme spread of three different
targets be the same as if all 30 rounds vere fired on the seme target? Further
experinentation is needed to answer such questions. If the data had been
analyzed vhile the test vas in proress, the quaait of data night have been
improved by eliminating the rmnadoness of data or by redesignin the exper-
frJln Dat. I BRomds
no.ael No. PPem erMtioi nut(cid:127)e
02 0. 30.93Ds1 20
02 C2 IM.93 B er 20
03 C3 Mo96Tracer 20
0o 4 M393 3.1 60
05 5 30.93 3.1 60
06 06 3.96 Tracer 60
30.93 Da 0
3M93 3.1 100
09 093 KL96 TuAer 100
10 an. M.93 Dm1 20
U1 me 3.93 Dm11 20
12 341 3 m303109936 TftrUu er 6200
(345 M193 3.1 60
15 ~ 30.9 6 Tracer 6
16 (3T7 X.93 3.1 100
(m8 10.93 Dm2 100
am9 1g96 Tracer 100
1290 ]34a2 30.91393 3DBma1l1l 220
21 b13 330211A99 363T.r1u1c er 2600
60
345 M1933.11U
346 mo.96 Truer 60
25 347 34933.11 100
26 3s0M933.12. 100
27 349 30.96 Tracer 100
2
nI.
IDnfa L Tn
Same of the teats were conducted with identical weapons (smem materialp
design and manufacturor),, saw am~muition,, and also same fixing rate. For
migiple,, Cl is identical to C2. 84-i1l-r pairs are Cli - C5, CT = 08j, IQ. - 42j,
to14,1 47 - NO., Ga. - (P42, %A~-i MP5 and Mq4 - CUB. It Is, logical that the
resul1tos uah as extram spread., mean radius and penetratiom by respective
gages would be identical because the test conditions mee Idenical. The eatial.
variations In results are not reasoa~ble based on the above teat conditions.
Since there is no consistency in the data and reasons are ukioun other than
Uhe mentioned round-to-roun~d ammunition variaticzu and lck of unique
(quantitative) measurements,. It Is recommnend~ed that curve fitting techniques
be utilized and consider the spread of data at the critical point rather than
wse rigid rules such asthe first data point that exceeds an extrou spread
of T Inches.
The extreme spread versus number of rounds Is sahom in Figures 28f thru 54.
The average spread of all tarets is used rather than the data ofý individuaL1
targets. A quadratic equation with method or least squares (I. e, a particular
case of method of weighted residuals) w~ used to correct the data further.
ft Is possible to use the@*courves in order to estimate the useful. life of
the barrel for any tolerance (chosen criteria) of extreme spread. 2he useful
life of the barrel In given in Table 11 for extreme spreads of T and 9 Inches.
This table thoan variatiocA not onl~y due to various manufacturers but also
between guns frnthe sawmainufacturer* The useful. life of weapons with
tracer ammunition Is more than the range of expyerimental, data that exlets
* andltherefore,, cannot be predictable. There are no attes~ta to extrapolate
the data because of unknown, behavior for larger number of rouns fired.
fThi table also ohmw that the useful. life of thu weapon varies from
5,150 to 21,14W0 roundse (or 30,600 if extrapolated Just outside Of theL range
for another gun# 2P2) for conventional amnuimition, provided the Allowance of
7 Inches of extreme spread criteria is chosen. The similar useful. life of
the barrels is 7#1214 to 29,058 romdAs for 9 inches extrams spread criteria,
* .
(extrapolation is not meaningful for the larger extreme, spread criteria).
The minimum service ife is Indicated for 347 and the naius for 02. The
useful. service life is given, in Table MU for the tests that am considered
to be identical.
In generlj, the variations are extensive and there Is no consistency.
It Is very difficult to predict what the results will be If human interference
(various soldiers) different field conditions and combat sa pressures are
involved.
Moreover, th ult n unity of data can make significant differences
in the end results. For exmple,, Figure 29 Is redrawn with lmess quantity of
data. This Is showin in Figure 55 (Punched Data svwp1~ed by Too hthen,
Appl.ication Engineering Directorate, OIN Thoms J. Roduman Laboratory).
The curve trends are quite different between Figures 29 mud5.
3
rot
1DI-A 01 0 l -VNV :
tn MM
PWv gI sR l u94R
I I IIEIII
MIM OF IDENTICAL TEST CONDITIONS
_ _ :
Life upto. *A ktroms Opmtd oft
weapon 7
Ci 16,610
C2 21(cid:127)8(cid:127)0 29,058
C4& 10,960 13,389
[ 10,060 '...13,700
C7 7,590 7,589
C6 1.0,96o 23,655
ma 18,81&o 23,,682
-12 30,6oo*
oiA 1~~1,950 1415
9S,1O 7T,3350
8,11(cid:127) ...... 9,786
___. __ _____
M7. 7,110 90v937
M(2 10,760 15,80U
5(cid:127),870 8,9n1
3X5 7,.10 10,380
X(7 5,150 7,3241
50,990 7,897
* Itrapolated
5