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VELOCITY AND PRESSURE EFFECTS ON PROJECTILES DUE TO VARIATION OF IGNITION
PARAMETERS

Richard Otis Culver
Monterey, California

VELOCITY AND PRESSURE EFFECTS ON PROJECTILES DUE TO VARIATION OF IGNITION
PARAMETERS

Richard Otis Culver, Jr.
and
Raymond Michael Burns

Thesis Advisor:
J. E. Sinclair

Thesis Co- Advisor:
G. A. Garrettson

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II. EXPERIMENTAL PROCEDURE

A. SEQUENCE OF EVENTS

While awaiting the arrival of the pressure transducer it was decided
to proceed with the velocity testing portion of the project. The firing
during this portion of the project was conducted using a U.S. M1904A3
rifle of Remington manufacture , with a 24" barrel of uniform twist, one
turn in ten inches and having two lands and grooves. The modified for-
ward primed cases were constructed from standard military .30-06 caliber
rifle cases.

Muzzle velocity was measured by means of a digital ballistic chrono-
graph and a set of screens placed five feet apart. The bullet passing
through the first screen breaks contact and allows the chronograph to
start counting. When the bullet breaks the second screen the chronograph
stops counting. The time of flight of the bullet between the screens is
measured, and read out on a visual display using light emitting diodes.
A computer program (see p. 64) translates time of flight measurements into
ft/s readings. The chronograph was checked for accuracy by firing a
series of shots using match ammunition of known velocity as published by
Frankford Arsenal, and the results were within ten ft/s of the published
velocity .

Upon arrival of the transducer it was mounted in a barrel of .30-06
caliber and the system test fired. Upon extraction of the case it was
found that the chamber had been reamed to the wrong size and the barrel
was unsatisfactory for experimental purposes. Due to time limitations
the only suitable barrel available was a 7.62mm; this was the barrel in
which the transducer was ultimately mounted. Although the first portion

26 ,

of the project had been conducted at an outside range it was decided to
conduct both the velocity and pressure measurements in an indoor labora-
tory where power was available for the oscilloscope. It was discovered,
however, that the chronograph would not function within the confines of
the laboratory for same as yet unexplained reason. Thus, the velocity
measurements had to be once again taken at the outdoor range, where the
chronograph functioned properly. The independent measurements were com-
patible since the same barrels and loads were used in both cases. The
chronograph did function for some seven rounds indoors before it became
necessary to conduct the firing outdoors, and these shots were consistent
with those fired at the outdoor range. Although it was desired to obtain
all information on a rifle of one caliber, due to the circumstances only
velocity information was obtained for the .30-06 while both velocity and
pressure information was obtained for the 7.62mm.

B. CONSTRUCTION OF THE FORWARD PRIMED CARTRIDGE CASES

A detailed description of the construction of the forward primed car-
tridge cases was deemed necessary because of the difficulties encountered
in initially making the modified cases. The construction process was one
of trial and error originally and the best results were realized from the
following procedures. The first sets of cases were constructed from
standard military .30-06 caliber rifle cases. The cases were deprimed,
primer rockets cleaned and then threaded. The initial cases were con-
structed with 3/32" brass tubes which were threaded with a 4-40 die and
the cases were threaded with a 4-40 tap without first enlarging the flash
hole in the primer pocket. The tube was held in a small vice and the die
was slowly and carefully used to thread the end, backing off frequently

to insure that the threads were not crooked. The tube was then removed
from the vice and tried in the case before catting it to size. If the
threads were so long as to allow the tube to protrude into the primer
pocket the tube was removed from the case and filed to the proper length
with a fine file. Once the tuba had been properly threaded it was
replaced in the vice and cut off to 1 5/8" with a razor saw. A small
jeweler's screwdriver with xemovable blades was modified to act as a tool
to install the finished primer tuba. The screwdriver was disassembled
and the collet-like jaws were heated to a cherry red with a small torch.
The jaws were allowed to cool with quenching, leaving them soft enough
to drill. The screwdriver body was then inserted in the vice and drilled
to size with a 1/4" electric drill, lb use this tool to insert primer
tubes, the tubes were inserted in the end of the screwdriver by hand, the
threaded end of the tube out. The collar of the screwdriver was then
tightened down on the tube. Tne tool and tube were then inserted in the
case and the tube screwed into the threads in the primer pocket. By
continuing to turn the tool and gently withdrawing it at the same time
the tube was left firmly screwed into the primer pocket.

After the initial tests it was thought that the small inside diameter
of the 3/32" tube was not allowing sufficient flash to reach the powder
charge to insure optimum results. For this reason a switch was made to
1/8" tubing. All procedures remained the same, except that now a 6-32
tap and die was used, and flash holes were pre-drilled in the cases with
a 5/52" drill to facilitate the threading of the flash holes.

All .30-06 cases were then primed with CCI Magnum, large rifle primers
and the appropriate powder charges added. Projectiles used in all con-
figurations were standard 173 grain boat-tail match bullets as manufactured

by Frankford Arsenal.

The procedures for manufacturing the forward primed 7.62mm cases
remained the same with the following exception. The advice of Mr. Keith
was taken to reduce the length of the primer tube to approximately half
the length of the cartridge case. For the 7.62mm NATO cartridge this
worked out to be .9 inches. This change was made based on the optimum
results obtained when Mr. Keith was working on forward priming during
World War II.

C. TYPES OF POWDERS USED

The firing done with the .30-06 was carried out using three different
powders. IMR 4350 , 4320, and 4064 were used in varying amounts and com-
binations in collecting velocity data during this portion of the testing.

The firing done with the 7.62mm was carried out using six different
powders. The powders used were IMR 4350, 4320, 4227, 4064, 3031, and 4895,
lb gain good comparative data a lot of 7 . 62mm match ammunition of proven
excellence and uniformity was selected. The best available lot was XM118,
Lot 12015, Lake City Army Ammunition Plant. This ammunition was issued
for competition at the 1964 National Matches held at Camp Perry, Ohio.
The brochure issued at the National Matches by the Army Material Command
specified that this ammunition contained 48 grains of LMR 4895 [4] . Upon
checking the actual powder charge it was found to contain 41.5 grains of
a powder that closely resembled IMR 4320. A charge of 48 grains of
LMR 4895 would not fit in the cartridge case. Since the tests were com-
parative in nature the single powder loads were based on the powder with
which the 1964 NM loads were assembled. The powder was referred to
throughout the project as the 1964 NM powder.

Figure 9. Construction of the forward primed cartridge case.

173 grain bullet

1/8" O.D.-

primer tube

. N ■>.*■! «•

3/32" I.D.

Primer pocket threaded with 6-32 tap

Duplex and triplex loads were assembled with powders of known charac-
teristics since no currently produced ammunition would provide a meaning-
ful comparison. Subsequent lots of 7.62mm match ammunition available for
use utilized a ball type powder which gave very erratic performance as
outlined in the results of the tests. Tests were made using this powder
(1968 NM) both with and without primer tube. It is believed that this
was caused by the very fine-grained powder filtering into the primer tube
in unpredictable amounts.

Better results with primer tube retention were obtained with the
7.62mm ammunition than with the .30-06 ammunition. Only one'primer tube
separation was experienced throughout the entire series of 7.62mm. tests.
The higher retention was attributed to the reduction in length of the
tube thus reducing the effective lever arm, and the fact that more
experience had been gained in assembling the cartridge by this time.

Ill . PRESENTATION OF DATA

A. VELOCITY DATA FOR .30-06 CALIBER RIFLE

The velocity data for this portion of the project was taken for ten

different loads, each load consisting of ten rounds. The testing was

conducted on two sizes of primer tubes , and control charges with no

primer tubes were fired for a basis of measuring any differences in the

modified cases. The following loads were fired as noted in the

appropriate tables:

Table I Small Primer Tubes (3/32" Tube)

Load No. NO. of Grains Type of Powder Comments

control charge, no tube

tube installed

top layer, slowest burning
bottom layer, fastest burning

top layer, slowest burning
middle layer, medium burning
bottom layer, fastest burning

Table II Large Primer Tubes (1/ 8 " Tube)

5 50 IMR 4350 control charge, no tube

6 50 IMR 4350 tube installed

7 25 IMR 4350 top layer, slowest burning

25 IMR 4064 bottom layer, fastest burning

8 17 IMR 4350 top layer, slowest burning
17 IMR 4320 middle layer, medium burning
17 IMR 4064 bottom layer, fastest burning

Table III Large Primer Tubes (1/8" Tube)
9 50 IMR 4320 control charge, no tube

10 50 IMR 4320 tube installed

IMR 4350

IMR 4064

IMR 4350

IMR 4320

IMR 4064

Velocity

Data f co

msec

Lead

ft/s

2.06

2427

2.10

2381

2.08

2404

2.15

2326

2.06

2427

2.07

2415

2.10

2381

2.09

2392

2.06

2427

2.08

2404

TABLE I
.30-06 Using 3/32" Primer Tube

Load 2

msec

ft/s

2.05

2439

2.10

2380

2.03

2463

2.02

2475

2.06

2427

2.04

2451

2.05

2439

2.06

2427

2.08

2402

2.04

2451

Avg. Velocity 2398

Avg. Velocity 2435

Load 3

Load 4

msec

ft/s

2.07

2415

2.05

2439

2.00

2500

1.95

2564

1.97

2538

1.94

2577

2.00

2500

1.97

2538

2.01

2487

2.00

2500

Avg. Velocity 2506

msec

ft/s

1.91

2618

1.87

2674

1.93

2590

1.95

2564

1.92

2604

2.02

2475

1.92

2604

1.93

2590

1.91

2618

1.91

2618

Avg. Velocity 2596

TABLE II

Velocity Data for .30-06 Using 1/8" Primer Tube
Load 5 Load 6

msec

ft/s

2.05

2439

2.02

2475

2.04

2451

2.06

2427

2.06

2427

2.05

2439

2.08

2404

2.03

2463

2.08

2404

2.05

2439

Avg. Velocity 2437

msec

ft/s

2.02

2475

2.06

2427

2.02

2475

2.04

2451

2.02

2475

2.01

2488

2.01

2488

2.02

2475

2.01

2488

2.02

2475

Avg. Velocity 2472

Load 7

Load 8

msec

ft/s

1.94

2577

1.95

2564

1.95

2564

1.96

2551

1.94

2577

1.94

2577

1.92

2604

1.93

2590

1.94

2577

1.94

2577

Avg. Velocity 2576

msec

ft/s

1.85

2703

1.89

2646

1.87

2674

1.89

2646

1.90

2632

1.88

2660

1.88

2660

1.89

2646

1.89

2646

1.88

2660

Avg. Velocity 2657

TABLE III
Velocity Data for .30-06 Using 1/8" Primer Tube
Load 9 Load 10

msec ft/s . msec ft/s

1.91

2618

1.93

2591

1.89

2646

1.83

2646

1.87

2674

1.86

2688

1.91

2618

1.91

2618

1.89

2646

1.87

2674

1.87

2674

1.87

2674

1.90

2632

1.86

2688

1.89

2646

1.89

2646

1.84

2717

1.87

2674

1.85

2703

1.86

2688

Avg. Velocity 2642 Avg. Velocity 2674

B. VELOCITY DATA FOR 7.62mn CALIBER RIFLE

The velocity data for this portion of the project was taken for ten

different loads, each load again consisting of ten rounds. Testing was

conducted for only one size primer tube (1/8") , and two loads with no

primer tubes were used as reference points. The following loads were

fired as noted in the appropriate tables:

TABLE IV

Load No. N o. of Grains Type of Powder Comments

1964 National Match, no tube

1964 NM, tube installed

top layer, slowest burning
bottom layer, fastest burning

top layer, slowest burning
middle layer, medium burning
bottom layer, fastest burning

41.5

IMR 4895

41.5

IMR 4895

43.5

IMR 4895

30.0

IMR 4350

14.1

IMR 4227

TABLE V

14.0

• IMR 4350

14.0

IMR 4320

14.0

IMR 4064

16.1

IMR 4320

14.8

IMR 3031

9.9

IMR 4227

20.8

IMR 4320

14.8

IMR 3031

6.9

IMR 4227

14.0

IMR 4350

14.0

IMR 4064

•

14.0

IMR 3031

TABLE VI

44.5

IMR 4895

44.5

IMR 4895

1964 NM, without tube
1964 NM, tube installed

TABLE IV

Velocity Data for 7.62mm Using 1/8" Primer Tube
Load 1 Load 2

msec

ft/s

1.90

2632

1.90

2632

1.90

2632

1.91

2618

1.95

2564

1.95

2564

1.95

2564

1.93

2591

1.91

2618

1.92

2604

Avg. Velocity 2602

msec

ft/s

1.96

2551

1.96

2551

1.98

2525

1.96

2551

1.98

2525

1.97

2538

2.01

2487

1.97

2538

1.98

2525

1.96

2551

Avg. Velocity 2534

Load 3

Load 4

msec

ft/s

1.89

2646

1.88

2660

1.88

2660

1.88

2660

1.90

2632

1.87

2674

1.88

2660

1.91

2618

1.87

2674

1.88

2660

Avg. Velocity 2654

msec

ft/s

1.89

2646

1.91

2618

1.92

2604

1.92

2604

1.90

2632

1.89

2646

1.91

2618

1.88

2660

1.90

2632

1.89

2646

Avg. Velocity 2631

TABLE V

Velocity Data for 7.62mm Using 1/8" Primer Tube
load 5 load 6

msec

ft/s

2.15

2336

2.12

2358

2.12

2358

2.12

2358

2.16

2314

2.14

2336

2.12

2358

2.16

2314

2.15

2336

2.13

2347

Avg. Velocity 2342

msec

ft/s

1.93

2591

1.92

2604

1.92

2604

1.91

2618

1.94

2577

1.92

2604

1.93

2591

1.90

2632

1.92

2604

1.94

2577

Avg. Velocity 2600

Load 7

Load 8

msec

ft/s

1.92

2604

1.89

2646

1.90

2632

1.91

2618

1.87

2674

1.91

2618

1.90

2632

1.92

2604

1.89

2646

1.92

2604

Avg. Velocity 2628

msec

ft/s

1.86

2688

1.84

2717

1.87

2673

1.87

2673

1.85

2703

1.84

2717

1.88

2660

1.86

2688

1.85

2703

1.86

2688

Avg. Velocity 2691

TABLE VI
Velocity Data for 7.62mm Using 1/8" Primer Tube
Load 9 Load 10

msec ft/s msec ft/s

1.86

2688

1.85

2703

1.86

2688

1.83

2732

1.88

2660

1.85

2703

1.87

2674

1.85

2703

1.86

2688

1.84

2717

1.85

2703

1.85

2703

1.87

2674

1.86

2688

1.87

2674

1.87

2674

1.85

2703

1.82

2747

1.83

2732

1.86

2688

Avg. Velocity 2696 Avg. Velocity 2699

C. PRESSURE DATA FOR 7.62mm CALIBER RIFLE

Pressure data was obtained for match ammunition both with and without
the primer tube in place, and for a single duplex load and five triplex
loads of various charge configurations. A minimum of five time-pressure
curves were taken for each load.

The oscilloscope was set for two volts/cm or 10,000 psi/cm and the
base line or zero pressure line for all shots was as indicated in
Figure 11. The time or horizontal axis on the oscilloscope was set for
.1 msec/cm. Since time of flight in the barrel is approximately .001
second (Figure 10) the bullet exited the barrel at the right edge of
the photographs with relatively low pressures.

1. 1964 Match Ammunition With and Without Primer Tube

This powder load was reported to contain 48 grains of IMR 4895,
producing a chamber pressure of 44,000 psi [4]. When examined the load
was found to contain 41.5 grains of powder. The average peak pressure
obtained for this load was 40,000 psi (Figure 12) .

The same powder charge with primer tube installed averaged
33,700 psi (Figure 13) .

An extra grain of powder was added to the conventional case for
a total of 42.5 grains. The average peak pressure for this load was
41,000 psi (Figure 14) .

The same load of 42.5 grains with primer tube installed averaged
36,000 psi (Figure 15) . No velocity data was obtained for this
particular load.

The load was increased another grain to 43.5 grains, and with
primer tube installed the average peak pressure obtained was 42,000 psi
(Figure 16) .

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Figure 11. Base line setting for all pressure
readings. Vertical axis (pressure)
scale setting at 10,000 psi/cm.
Horizontal axis (time) scale setting
at .1 msec/cm.

Figure 12. Load No. 1, Table IV, 41.5 grains
of 1964 NM powder. Average peak
chamber pressure 40,000 psi.

Figure 13. Load No. 2, Table IV, 41.5 grains
of 1964 NM powder with primer tube
installed. Average peak chamber
pressure 33,700 psi.

Figure 14. 42.5 grains of 1964 NM powder,
without primer tube installed.
Average peak chamber pressure
41,000 psi.

Figure 15. 42.5 grains of 1964 NM powder, with
primer tube installed. Average peak
chamber pressure 36,000 psi.

Figure 16. load No. 3, Table IV, 43.5 grains of
1964 NM powder with primer tube
installed. Average peak chamber
pressure 42,000 psi.

The load was increased to 44.5 grains with primer tube installed
and the average peak pressure obtained was 47,700 psi (Figure 17) . The
same load without tube exceeded 50 , 000 psi on all shots (Figure 18) .
The exact pressure was undetermined since it peaked off -scope due to the
two volts/cm setting and the ten volt limitation of the amplifier.

2. 1968 Match Ammunition With and Without Primer Tube

No data was available to determine what type of powder was used
in the 1968 match ammunition other than the fact that it was ball type
powder. The same load was used in shots with and without the tube
inserted in the case. Without the tube the average peak pressure
obtained was 39,500 psi (Figure 19) and the readings were very consistent,

With the tube inserted the average peak pressure obtained was
34,300 psi (Figure 20) . Although the pressure averaged 5,000 psi lower,
the data obtained was very inconsistent, ranging from 28,000-42,000 psi.
This may be explained by fine grains of powder dropping into the primer
tube prior to firing.

3. Duplex Load With Primer Tube

Only one duplex load was tested and it consisted of 30.0 grains
of IMR 4350 as the slower burning top layer, and 14.1 grains of IMR 4227
as the faster burning bottom layer. This load was by far the most con-
sistent load tested, every shot having a maximum peak pressure of
48,000 psi (Figure 21) .

4. Triplex Loads With Primer Tube

Five triplex loads were tested using various powder types and
loads. Triplex Load No. 5, Table V, consisted of 14 grains each of
IMR 4350, 4320, and 4064. These powders were layered from top to bottom

Figure 17. Load No. 10, Table VI, 44.5 grains
of 1964 NM powder with primer tube
installed. Average peak chamber
pressure 47,700 psi.

■Mco^oooww;

Figure 18. Load No. 9, Table VT, 44.5 grains
of 1964 NM powder without primer
tube installed. Average peak
chamber pressure exceeds 50,000 psi.

Figure 19. 1968 NM powder without primsr tube
installed. Average peak chamber
pressure 39,500 psi.

Figure 20. 1968 NM powder with primer tube
installed. Average peak chamber
pressure 34,300 psi.

Figure 21. Load No. 4, Table IV, Duplex load

with primer tube installed. Average
peak chamber pressure 48,000 psi.

Figure 22. Load No. 5, Table V. Triplex load

with primer tube installed. Average
peak chamber pressure 30,500 psi.

in order of increasing "quickness," the IMR 4350 was the "slowest" and
the IMR 4064 the "quickest" of the three powders. This load gave an
average peak pressure of 30,500 psi (Figure 22) .

Triplex Load No. 6, Table V, was made up of 16.1 grains of
IMR 4320, 14.8 grains of IMR 3031, and 9.9 grains of IMR 4227 in
increasing "quickness" from top to bottom. This load of 40.8 grains
gave an average peak pressure of 42,000 psi (Figure 23) .

Triplex Load No. 7, Table V, was made up of 20.8 grains of
IMR 4320, 14.4 grains of IMR 3031, and 6.9 grains of IMR 4227 for a
total load of 42.5 grains. This load gave an average peak pressure of
42,500 psi (Figure 24) .

Triplex Load No. 8, Table V, consisted of 14 grains each of
IMR 4350, 4064, and 3031. This load of 42 grains gave an average peak
pressure of 34,000 psi (Figure 25) .

The last triplex load consisted of 20.8 grains of IMR 4320, 14.8
grains of IMR 3031, and 9.9 grains of IMR 4227, for a total load of
45.5 grains. This particular load exhibited all the classical signs of
excessive pressure including loose primer and difficult extraction. The
pressure exceeded 50,000 psi and it was decided to not test this load
any further (Figure 26) .

Figure 23. Load No. 6, Table V. Triplex load

with primer tube installed. Average
peak chamber pressure 42,000 psi.

Figure 24. Load No. 7, Table V. Triplex load

with primer tube installed. Average
peak chamber pressure 42,500 psi.

Figure 25. l£>ad No. 8, Table V. Triplex load

with primer tube installed. Average
peak chamber pressure 34,000 psi.

Figure 26. 45.5 grains. Triplex load with

primer tube installed. Pressures
in excess of 50,000 psi resulted
in loose primer and extraction
difficulty .

IV. CONCLUSIONS

A. FINDINGS

1. Pander Charges with Single Type of Powder

When using a single type of powder of a given grain weight, signif-
icantly lower pressures were obtained with the forward priming technique,
than when conventional priming techniques were used. Velocities for the
same weight of powder were essentially the same for either priming
technique.

The above fact allowed the practice of adding small carefully
weighed amounts of additional powder to the forward primed cartridges to
bring the pressure curve back to a normal level. When the pressure of
both cartridges was again equal, the forward primed cartridge gave the
highest velocity. The same amount of carefully weighed powder could be
added to the conventional cartridge, however the attendant increase in
pressure appeared to be excessive. When more powder was added to the
forward primed cartridge and the pressure gradually brought up past its
original level, but kept within normally accepted pressure limits
(48,000-50,000 psi) for the 7.62mm NATO round, velocities increased to
approximately 2700 ft/s, a gain of 100 ft/s over the original load. The
same amount of additional powder was added to the conventional cartridge.
This resulted in the same velocity gain as the forward primed round, but
the pressure exceeded the scale limitation of the grid and the charge
amplifier, in this case, 50,000 psi.

The above results were obtained using a tubular grained IMR powder.
The same experiment was performed using the ball powder currently being
used in 7.62mm Match Ammunition, giving erratic results. Seme very low

pressure readings were obtained, but seme approached the same level as
the cartridge without the primer tube. Efforts were then made to load
the cartridges as carefully as possible by leaving the primer tubes
plugged until the powder charge was properly in place. This practice
gave the same erratic results as the first batch of ball powder car-
tridges. The erratic pressure results were felt to be the result of an
unpredictable amount of the tiny grains of ball powder filtering down
into the primer tube. Further experimentation with ball type powders
was dropped due to time limitations, however, it is possible that some
excellent results might be obtained by using a combustible cover (such
as cellophane) over the end of the primer tube, as some of the lowest
pressure readings were obtained with the ball type powder.
2. Multiplex Powder Charges

When relatively slow burning powders of the type normally
associated with the loading of large bore rifles were used (i.e., IMR
4350, IMR 4320, IMR 4064, and IMR 3031) in proportional amounts and
arranged in order of burning speed (slowest burning ignited first) no
problems were encountered and greatly reduced pressures were achieved.

With the .30-06, duplex and triplex charges increased muzzle
velocities a significant amount. Since no pressure instrumentation was
available for the .30-06, unfortunately no pressure data is available.

The 7.62mm achieved much lower pressures, -but only at the expense
of reduced velocities. No additional powder could be added using the
powders mentioned in paragraph 1 above, because the maximum case volume
had been exceeded.

Switching to faster burning powders for duplex and triplex loads
resulted in higher velocities, but the advantage of low pressure peaks
was lost. One such triplex loading in the 7.62mm exhibited all the clas-
sic signs of pressure including loosened primer, gas leakage around the
primer, bright ejector mark on the base of the cartridge, expanded case
head and difficult extraction. Further experimentation was dropped
along these lines in the interest of safety and practicality.

B. OPINIONS

1. Reduction of Pressure with Primer Tube

The reduction of pressure utilizing forward priiriing techniques is
believed to be due to several factors. The energy of the primer alone is
usually sufficient to propel the projectile a short distance into the
bore. The addition of the primer tube accomplishes two things. First it
directs the energy of the primer at the base of the projectile, and second
it serves to ignite the very forward end of the powder charge. This
causes the projectile to be propelled into the bore prior to the complete
combustion of the powder charge. This increases the effective volume of
the combustion chamber. If the classic formula PV = nRT is taken to be a
valid approximation here, an instantaneous evaluation of the results of
increasing the volume, with all other variables considered to be essen-
tially constant at that particular instant, would of necessity require
that the pressure be reduced. .

Once the projectile starts to move, the relative volume increases
rapidly, thus further decreasing the pressure before the powder charge is
completely consumed.

Even though the printer tube does occupy some of the internal
volume of the case, a condition that should raise the initial pressures,
the distance the projectile is moved down the bore prior to the combus-
tion of the powder charge more than compensates for the small decrease
in volume of the aartridge case due to the primer tube.

The reduction of pressure should also have the added beneficial
effect of lower bore temperatures. A reduction in bore temperature would
be very beneficial in cutting down on bore erosion, especially in weapons
with a high cyclic rate of fire.
2. Multiplex Powder Charges

Theoretically it should be possible to adjust the powder charge
burning rate so that it would become progressively faster as the projec-
tile proceeds down the bore, thus allowing a lower pressure peak of
longer duration giving the bullet a constant push all the way down the
bore. The fact that higher velocities were obtained with the .30-06 and
not with the 7.62mm when utilizing the same powders in similar proportions
(although not in the same amounts, due to the smaller case capacity of the
7.62mm) suggests the possibility that there is an optimum case volume for
a given bore size. The long flat pressure curve obtained with the 7.62mm
(see figure 22) shows excellent promise, but the fact that the case was
filled to absolute capacity precluded the addition of enough powder to
take advantage of pressure reduction in the pursuit of high velocities.
A cartridge the size of the .300 Winchester should provide an ideal
vehicle to prove the theory.

A word of caution is due here. When using charges of several
different burning rates, the charge must be sufficiently compressed to
prevent the charges from shifting or mixing. The second note is one of

technique. Often compressed powder charges are mentioned that just do
not seem to want to fit in the case. Generally such charges are dropped
into the case through a long tube, and then the case is gently tapped on
the side near the base to cause the powder to settle. When triplex
charges are put in it is sometimes necessary to go through this procedure
for each layer of powder.

The multiplex charge idea deserves further investigation, however
time and the lack of a rifle of sufficient case capacity adapted to pres-
sure instrumentation prevented extensive research into this aspect of
forward ignition. The multiplex idea would seem to be ideally suited to
large caliber naval guns, field artillery, and tank guns. Such guns
already utilize a perforated primer tube and it should pose no great
problem to use a solid primer tube filled with black powder or some simi-
lar highly combustible material to insure uniform positive ignition.
Charges of different burning rates could be identified by different
colored powder bags, or the bags could be numbered in loading sequence.
3. Production Techniques and Refinements

In reality the process of manufacturing small arms ammunition
with primer tubes could be easily solved. . A slightly deepened primer
pocket would allow the use of a tube with a primer pocket sized flange to
be pressed into the case from the rear. This would allow for rapid pro-
duction and avoid any case or tube threading problems. The tube could be
of thinner gauge metal to cut down on both internal case volume reduction
and total case weight.

A further refinement would be the construction of the primer tube
out of a combustible plastic such as. cellulose nitrate, treated so that it
would resist ignition by the primer, but would ignite at the combustion

temperature of the powder charge. This teclinique would allow higher
velocities frcm cases such as the 7.62niri NATO cartridge that have limited
case capacity , since the tube occupies internal case volume that would
house several additional grains of powder.
4. Possible Applications

As suggested above, the system is adaptable to both small arms
and large bore weapons including tank guns, aircraft cannon, artillery,
and naval guns. In field artillery current ballistics could be main-
tained with a great savings in weight and portability due to the low
pressures involved. The mounting system and barrels on aircraft cannon,
naval guns, and tanks could be lighter, with an attendant weight savings
for the entire vehicle.

For a given set of ballistics, bore erosion would be less, since
pressure and thus bore temperatures would be less. This would allow
higher rates of fire, or with normal rates of fire, longer time periods
would be possible before it became necessary to reline bores or replace
barrels.

Flat trajectory weapons such as tank guns could be given higher
velocity, extending their effective range and cutting down on range
estimation error.

C. IMXMMENDATIONS

It is recommended that further research be conducted with forward
priming techniques to include work with duplex and triplex charges with
a cartridge of sufficient case capacity to take advantage of progressive
burning rates of properly arranged powder charges. As mentioned before,
the .300 Winchester should provide sufficient case capacity for a
meaningful research project.

It is further recanroended that the research be expanded to include
105nm artillery pieces, five inch naval guns, and 20mm aircraft
cannon.

APPENDIX A

List of Equipment Used

Pressure Transducer: Kistler Model 607A Quartz Pressure Transducer
Charge sensitivity 0.195 pCb/psi and range to 70,000 psi

Amplifier: Kistler Model 504 Universal Dial-Gain Charge Amplifier.
Produces full-scale outputs from 1 psi per volt to 50,000 psi
per volt for any charge input from .1 pCb per psi to 10 pCb per
psi input sensitivity

Oscilloscope: Tektronix Type 515A Oscilloscope mounted with Polaroid
scope camera

APPENDIX B

Photographs of Equipment Set-up

Oscilloscope and camera, amplifier, rifle on mounting

Transducer mounting collar, transducer, amplifier

Mounted transducer
hooked to amplifier.

Bullet trap with
splash shield located
20 feet from the
muzzle .

■XW MW; ;.;.;.;.%;.;.•;•

Transducer mounted in chamber.

Firing conducted at outdoor range. Chronograph (on
bench) hooked up to screens located 5 feet apart.

Single screen hook-up. Screen consisted of 35rrm
film with continuous metallic paint pattern inside.

3
B

■H

•H

■8

0223. WP12) 'CULVER BOX C«
I
iCOO.O

iJCB (2D12,

0=5.0

F=100l

S = 1.0

0=5

DO 70

WRITE

DO BO

V=D^'F

WRITE

S = S+1

CONTII

D=D + 1

CC NTH

STOP

FORMAT ( '0' , 'FREQUENCY RANGE 100,000 HZ',//,' ■

1 SCRE!

•SCRE

FORMA'

END

83
70

1000

]

2000*

M=l,20
{ 6, 1000)
J=l,999
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( 6,2000)
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EN READOUT' )
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//

BIBLIOGRAPHY

1. Hatcher, J. S., Hatchers Notebook , 3d ed., p. 300-333, The Stackpole

Company, 1966.

2. Keith, Elmer, "Duplex loading," The American Rifleman, p. 19-21,

November 1946.

3. Lyman Reloading Handbook , 45th ed., p. 205-218, Lyman Gunsight

Products , 1970.

4. 1964 National Match Rifle , p. 13, U. S. Army Materiel Command,

5 April 1963.

5. Vfeapons Systems Fundamentals , NAVWEPS OP 3000, V. 2, p. 86-96,

U. S. Government Printing Office, 1963.

6. Yard, E. M. , "Fundamental Ballistics," The Handloader Magazine ,

V. 1, p. 42-44, May-June 1966.

INITIAL DISTRIBUTION LIST

No. Copies

1. Defense Documentation Center 2
Cameron Station

Alexandria, Virginia 22314

2. Library, Code 0210 2
Naval Postgraduate School

Monterey, California 93940

3. Ground Combat Branch 2
Marine Corps Development and Educational Center

Quantico, Virginia 22134

4. Professor J. E. Sinclair, Code 61Sn 1
Department of Physics and Chemistry

Naval Postgraduate School
Monterey, California 93940

5. Assistant Professor G. A. Garrettson, Code 61Gr . 1
Department of Physics and Chemistry

Naval Postgraduate School
Monterey, California 93940

6. Mr. Elmer Keith 1
Salmon, Idaho 83467

7. Virginia Military Institute 1
Physics Department

Lexington, Virginia 24450

8. Major Richard O. Culver, Jr., USMC 1
1502 Fortner Street

Dothan, Alabama 36301

9. Captain Raymond M. Burns, USMC 1
376E Bergin Drive

Monterey, California 93940

UNCLASSIFIED

Security Cla ssification

DOCUMENT CONTROL DATA -R&D

lS ecun,y c ,*; si „c ation of title, body o< ehstroc, and indexlnj annotation n.us, be antered ,W>en *. over.// ,epor, /. c balded)

UGIN a TING ACTIVITY (Corporate author)

aval Postgraduate School
bnterey, California 93940

21. RtPORT SECURITY C L A SSI F I C A T I ON

Unclassified

2b. CROUP

EPORT TITLE

'elocity and Pressure Effects on Projectiles Due to Variation of Ignition Parameters

5ESCRIPT1VE NOTES (Type ol report end. inclusive dates)

(tester's The5is.;_D£cem 1 ,y,r 1972

fuTHORlSl (First name, middle initial, laat r.nme)

Richard Otis Culver, Jr.
Raymond Michael Burns

itPOHT DATE

)ecember 1972

CONTRACT OR GRANT NO.

PROJEC T NO.

7«. TOTAL NO. OF PACES

7b. NO. OF REFS

9C. ORIGINATOR'S REPORT NUMBEP.(S)

9b. OTHER MEPORT NOISI (Arty other numbers that may be caal&iod
thla report)

DISTRIBUTION STATEMENT

Approved for public release; distribution unlimited.

. SUPPLEMENTARY NOTES

2. SPONSORING MILITARY ACTIVITY

Naval Postgraduate School
Monterey, California 93940

ABSTR AC T

The effect of varying the point of ignition of the powder charge within a
cartridge case was investigated with respect to both pressure and velocity. By
installing a small tube in the base of the cartridge case it was possible to
transfer the primer flash to the forward part of the case. Ignition of the pow-
der charge at the top instead of the base gave lower chamber pressures by as
much as 6,300 psi and increased muzzle velocity by 35 ft/s. When additional
powder was added to obtain the same chamber pressure as a conventionally primed
cartridae, muzzle velocities increased by 50 ft/s. Where the pressure was
brought^up past the original level, but kept within normally accepted limits for the
7.62mm NATO round, velocities increased by 100 ft/s over the original load. In
order to shape the pressure curve, different loading schemes were tested. Var ^ us
amounts of powders and powders of different burning rates were layered within the
same case, the slowest burning powder being ignited first. Lower Pressures and
flatter pressure peaks were realized from these configurations. The chamber
pressure was reduced by 6,000 psi and the muzzle velocity increased by 100 ft/s.

JV) I NOV ♦si'? /O

~>/N 0101 -807-681 1

(PAGE 1)

UNCLASSIFIED

Security Cl»*mification

A-81408

UNCLASSIFIED

Security ClBesifirKticm

key *onoj

small-arms
forward priming
cartridge case
powder charges
chamber pressure
ammunition
ordnance

DD , f .T..1473 « BACK1

S/N 0101 -807-6821

RO LEI WT

UNCLASSIFIED

Security Classification

A- 3 1 409

V L 3 i 12

C J» ** o

Culver

Velocity and pressure
effects on projectiles
due to variation of i g-
nit ion parameters.

l':.I2G9

Culver

Velocity and pressure
effects on projectiles
due to vaiation of ig-
nition parameters.

thesC9258

Velocity and pressure effects

on project

3 2768 002 09825 3

3 DUDLEY KNOX LIBRARY