ARL-TN-0661 ● FEBRUARY 2015

US Army Research Laboratory

A Low Velocity 0.30-cal. Gun System

by Donald J Little

Weapons and Materials Research Directorate

Approved for public release; distribution is unlimited.
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ARL-TN-0661 ● FEBRUARY 2015

US Army Research Laboratory

A Low Velocity 0.30-cal. Gun System

by Donald J Little

Approved for public release; distribution is unlimited.
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May 2010–June 2011

4. TITLE AND SUBTITLE

A Low Velocity 0.30-cal. Gun System

5a. CONTRACT NUMBER

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5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Donald J Little

5d. PROJECT NUMBER

5e. TASK NUMBER

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

US Army Research Laboratory

ATTN: RDRL-WMP-E

Aberdeen Proving Ground, MD 21005-5066

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ARL-TN-0661

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13. SUPPLEMENTARY NOTES

14. ABSTRACT

An efficient method was needed to perform ballistic testing using 0.30-cal. Fragment Simulating Projectiles at or near 

subsonic velocity in order to screen new resin systems for advanced composite/ceramic armor scaled-down test coupons. This 

technical note outlines the custom gun system and testing methods developed to enable this ballistic testing.

15. SUBJECT TERMS

0.30-cal., low velocity, gun systems, fragment simulator projectiles, ballistic testing

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19a. NAME OF RESPONSIBLE PERSON

Donald J Little

a. REPORT

Unclassified

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410-278-6044

Standard Form 298 (Rev. 8/98)

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iii

Contents

List of Figures iv

List of Tables iv

1. Introduction 1

2. Approach 4

3. Experiments 8

4. Conclusion 13

5. References 14

Distribution List 15
iv

List of Figures

Fig. 1 0.30-cal. FSP................................................................................................1

Fig. 2 Standard brass case used to launch FSPs.....................................................3

Fig. 3 0.30-cal. FSP seated in test barrel................................................................4

Fig. 4 Testing barrel and barrel fixed in mount ......................................................5

Fig. 5 Custom cases and standard .30-06 cases.....................................................5

Fig. 6 Tape band fixed around end of custom case................................................6

Fig. 7 Resizing die with fragment and accompanying tools..................................6

Fig. 8 Seating tool used to precisely seat FSP projectile in gun barrel..................7

Fig. 9 Tissue seating ..............................................................................................8

Fig. 10 Ballistic range layout and parameters........................................................8

Fig. 11 Subsonic shock wave shield mounted forward of testing barrel ...............9

Fig. 12 0.30-cal. FSP launch velocity as a function of propellant load for custom 

case and 10.5-inches-long test barrel......................................................10

Fig. 13 0.30-cal. FSP launch velocity using standard components .....................11

List of Tables

Table V50 test data.................................................................................................12
1

1. Introduction

Rapid screening of new resin systems for advanced composite/ceramic armor 

dictated conducting ballistic experiments on scaled-down test coupons. These S-2 

glass/epoxy panels had a nominal areal density of 2 psf (9.75 kg/m2). These 

material systems were intended for service as back plates in ceramic composite 

armor systems and, because they were optimized as structural elements, their 

ballistic performance is rather low. The panel V50 testing was conducted 

according to Department of Defense standard MIL-STD-662F.

1 By characterizing 

V50 and the resulting delaminating damage near the ballistic limit for targets at a 

2-psf (9.75-kg/m2) areal density, a large number of resin candidates could be 

evaluated in a very short amount of time. Fragment Simulating Projectiles (FSPs) 

are useful for this type of screening because when employed at a low enough 

velocity no deformation (mushrooming) of the projectile occurs. The 0.30-cal.

FSP,

2

shown in Fig. 1, is an appropriate test projectile for the targets of this type.

Fig. 1 0.30-cal. FSP 
2

V50 testing for these evaluations required projectile impact velocities near the 

speed of sound in air. It is exceedingly difficult to get precise velocity control of 

gun-fired FSPs in this velocity regime using a conventional powder gun. This 

necessitated the development of a 0.30-cal. gun system tailored specifically to this 

velocity regime and projectile weight. Standard testing barrel lengths 

(18–30 inches) and standard commercial reloading propellants have shown they 

are not very efficient when testing at extremely low velocities with very light 

projectiles. One factor that inhibits velocity consistency when ballistic firing FSPs

is pressure buildup between the seated fragment and cartridge case tends to 

deform and collapse the case wall. This is due to the fragment being seated in the 

barrel bore separate from the cartridge case, which leaves a gap between the top 

of the cartridge case and seated fragment. This gap allows a space where chamber 

pressure can escape along the outside of the case and results in inconsistent 

chamber pressures, which in turn cause velocity control and velocity repeatability 

issues. This problem is more pronounced at higher pressures but is observed over 

all velocity ranges. By contrast, a standard cartridge has the projectile seated 

inside the neck of the case, and the pressure during propellant ignition presses the 

case against the chamber, thereby creating a pressure seal. Figure 2 shows 

deformation and carbon trails caused by chamber gas leaking around the cartridge 

case during an FSP shot. Figure 3 is a cross section of a test barrel loaded with a 

0.30-cal FSP to illustrate the problem area.
3

Fig. 2 Standard brass case used to launch FSPs

Carbon trails 

caused by 

gas leakage 

along outside 

of case.

Neck region 

on brass case 

showing 

damage 

caused by 

gas leakage.
4

Fig. 3 0.30-cal. FSP seated in test barrel

2. Approach

Past experience from FSP testing has shown the best approach to achieve very 

low velocities is to use a short barrel and a very fast burning propellant.

3 For these 

experiments, a barrel was made by cutting a 267-mm (10.5-inch)-long segment 

from a standard length 0.30-cal. testing barrel. The barrel has 3 lands and 3 

grooves and a twist rate of one turn for every 10 inches of length. The chamber of 

the barrel was reamed to accept a .30–06 Springfield case and threaded to accept 

the screw-on small-caliber percussion pin lab breech. Figure 4 shows the barrel 

and the barrel mounted in the test fixture that was used for testing.

Breech

FSP in bore

Brass case Test Barrel

Gap which permits chamber pressure loss
5

Fig. 4 Testing barrel and barrel fixed in mount

To mitigate case deformation and improve chamber pressure consistency, a thick 

rigid-wall custom cartridge case with a reduced internal volume was constructed 

from 17-4 PH stainless steel. The external geometry of the case was dimensioned 

to match a standard .30-06 case. The internal cavity was made by plunging a 

5.95-mm (15/64-inch)-diameter standard twist drill bit to the same depth as the 

inside of a standard .30-06 brass case. The thick body provides stiffness and 

rigidity and resists deforming and collapsing inward as pressure builds between 

the seated fragment and the cartridge case. Figure 5 shows a custom case made 

for these tests alongside a standard .30-06 brass case.

Fig. 5 Custom cases and standard .30-06 cases

The custom cases were heat treated to give them a temper that would yield 

durability and strength to allow repeated use. The cases were heated to 

900 °F and held for 1 h, then air cooled to ambient temperature. This process on 

17-4 PH stainless steel increases the tensile strength and produces a hardness of 

40-42 Rockwell C scale. 

The thick rigid-wall design of the custom case reduces chamber pressure loss but 

does not eliminate it entirely. An additional step performed while using the 

custom cases for these tests added a small band of masking tape around neck prior 

to loading it into the barrel. When the weapon was fired, the tape was forced 

Standard .30-06 case

Custom case

Standard .30-06 case

Custom case
6

down to the neck transition area of the case and formed a simple seal that helped 

contain pressures within the chamber area. The tape was approximately 5.08 mm 

(0.200 inch) wide and long enough to go around the case neck one time. Testing 

performed with and without the tape showed a definite improvement with velocity 

control when tape was used. The tape appears to provide the most benefit at lower

velocities and appears to fail with larger propellant loads and higher pressures.

Figure 6 shows a custom case pre- and posttest with tape in place.

Fig. 6 Tape band fixed around end of custom case

FSPs are individually machined parts where a certain amount of variation from 

part to part is normal. To improve consistency, prior to using them for these tests,

the FSPs were all passed through a steel resizing die to achieve a more consistent 

and uniform flare diameter, thus reducing variation of fit within the bore of the 

gun. The die is a commercially available swaging die with an internal diameter of 

7.848 mm (0.309 inch). Each FSP was gently tapped through the die using a 

copper rod punch and small hammer. Figure 7 shows the die and tools used to 

perform the resizing step.

Fig. 7 Resizing die with fragment and accompanying tools

 

Pre-test

Post-test

Resizing die

FSP Copper punch
7

Variation in FSP weight also contributes to velocity variations during testing. For 

these tests the FSPs were sorted by weight into groups of 10 that where within 

± 0.3 gr of one another. A group was then set aside for each panel to be evaluated. 

Another factor that will affect velocity is varying the FSP seating depth in the test 

barrel. FSPs must be seated in the gun at precisely the same depth for each test to 

achieve consistent velocities. A custom seating tool was made from a piece of allthread to perform this step. Two locking nuts and a stop washer were added to set 

the stopping point on the back of the barrel. This seating tool was then adjusted to 

seat the fragment 1.58 mm (1/16 inch) into the rifling of the gun. Figure 8 shows

the tools used to perform this step. 

Fig. 8 Seating tool used to precisely seat FSP projectile in gun barrel

The propellant used for these experiments was Bullseye smokeless pistol powder,

a very fast burning propellant manufactured by Alliant. The primer used was

Federal Gold Match large rifle percussion primers manufactured by Federal 

Ammunition.

Keeping the propellant charge evenly seated in the base of the case against the 

primer is also important factor in velocity consistency. A small piece of tissue of 

approximately 19.05 mm (0.750 inch) diameter was pushed down inside the case

on top of the propellant charge using a small wooden dowel (Fig. 9).

Tool with locking nuts and stop 

washer installed. Tool in barrel with fragment 

seated.
8

Fig. 9 Tissue seating

3. Experiments

The layout of the ballistic range for these experiments is shown in Fig. 10.

Fig. 10 Ballistic range layout and parameters

An Oehler chronograph system with 3 model 57 infrared screens spaced 

304.8 mm (12 inches) apart was used to collect and record velocity data for these 

tests. A few test shots were performed initially using 2 channels of orthogonal 

flash X-rays to measure fragment yaw characteristics in flight to confirm it was 

within acceptable levels (<5 degrees total). Since the test shots yielded yaw 

measurements well within the requirement, the bulk of testing was completed 

using chronographs only to capture velocity data.

Tissue 

Wood dowel 

Gun barrel

Shockwave arresting shield Chronograph velocity screens

Shotline

Panel Fixture

105” 8” 12” 12” 20” 26.5”

X-ray film planes side and orthogonal

X-ray heads

spaced 10” 

X-ray triggering screen

6”

Aluminum witness 
9

For this testing it was necessary to install a shock wave arresting shield directly in 

front of the first chronograph screen to get consistent triggering of the 

chronograph system. Since the velocity regime was subsonic (below the speed of 

sound in air), the shock wave traveled ahead of the projectile and caused false 

triggering of the chronograph screens. The shield was made from a piece of 

plywood with a 25.4-mm (1.0-inch) hole drilled in it. A piece of masking tape 

was placed over the hole for each shot to block the shock wave but allow the FSP 

to easily pass through. Figure 11 shows the shield in place forward of the testing 

barrel and in front of the chronograph screens.

Fig. 11 Subsonic shock wave shield mounted forward of testing barrel

Prior to starting panel evaluations, ballistic firing was completed to create a 

propellant reloading curve and create data to evaluate both velocity consistency 

and control. These data are shown in Fig. 12. For comparison, Fig. 13 contains 

0.30-cal. FSP testing data using standard 0.30-cal. reloading propellant with brass 

cartridge cases and an 889-mm (35-inch)-long test barrel.

Test barrel Shockwave shield 
10

Fig. 12 0.30-cal. FSP launch velocity as a function of propellant load for custom case and 

10.5-inch-long test barrel

100

200

300

400

500

600

1 2 3 4 5 6

15/64" ID Custom Case_Bullseye Propellant

y = -3.74x

2 +107x1 +119

Powder Weight (Grains)

Velocity ( m/s )

Velocity Curve
11

Fig. 13 0.30-cal. FSP launch velocity using standard components

The V50 evaluation on the panels required ballistic firing to continue until 3 partial 

penetrations (PPs) and 3 complete penetrations (CPs) within a 90 ft/s spread were 

obtained. The V50 is defined as the impact velocity at which the projectile has a 

50% probability of perforating (defeating) the target. A 0.51-mm (0.020-inch) 

2024-T3 aluminum witness plate was positioned 152 mm (6 inches) behind the 

target to determine the outcome of each shot. An impact is regarded as a CP, or 

loss, if the projectile or a resulting target fragment from impact creates a hole in 

the witness plate through which light can be observed. If an impact does not result 

in a CP, it is considered a PP or win. The Table contains V50 data collected using 

the custom case, barrel, and test methods outlined previously. 

800

900

1000

1100

1200

1300

1400

30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Standard Brass Case_IMR 4198 Propellant

y = 20x +244

PROPELLANT (Grains)

VELO

CITY (m/s)

Velocity Curve
12

Table V50 test data

AMB Shot No.

Propellant 

Weight 

(gr)

Velocity

(ft/s) Result FSP Weight (gr) Data Summary

9311 2 1087 PP 43.79 Panel 1

9312 2.4 1179 CP 43.67

9313 2.2 1137 PP 43.89

9314 2.3 1151 CP 43.88 Used for V50 calculation

9315 2.25 1133 PP 43.65 V50 ft/s = 1146

9316 2.3 1144 CP 43.82 Standard Deviation ft/s = 18

9317 2.25 1133 PP 43.74

9329 2.1 1090 CP 43.59 Panel 2

9330 1.9 1016 PP 43.78

9331 2 1069 PP 43.86

9332 2.05 1071 PP 43.83 Used for V50 calculation

9333 2.2 1087 CP 43.99 V50 ft/s = 1081

9334 2.1 1109 CP 43.77 Standard Deviation ft/s = 19

9335 2 1057 PP 43.73

9348 2.3 1147 PP 43.72 Panel 3

9349 2.5 1222 CP 43.75

9350 2.4 1170 CP 43.66 Used for V50 calculation

9351 2.3 1143 PP 43.81 V50 ft/s = 1177

9352 2.4 1180 PP 43.87 Standard Deviation ft/s = 31

9353 2.5 1202 CP 43.57

9354 2.5 1179 PP 43.71 Panel 4

9355 2.6 1228 CP 43.66

9356 2.55 1203 PP 43.72

9357 2.6 1248 CP 43.67 Used for V50 calculation

9358 2.55 1186 CP 43.64 V50 ft/s = 1190

9359 2.46 1181 CP 43.58 Standard Deviation ft/s = 22

9360 2.4 1164 PP 43.61

9374 2.2 1123 CP 43.88 Panel 5

9375 1.9 1028 PP 43.75

9376 2.05 1057 CP 43.78

9377 1.98 1060 CP 43.77

9378 1.85 930 PP 43.71 Used for V50 calculation

9379 1.9 1017 PP 43.51 V50 ft/s = 1035

9380 1.95 1041 CP 43.53 Standard Deviation ft/s = 21

9381 1.89 1007 PP 43.8

9382 2 1054 PP 43.65 Panel 6

9383 2.2 1107 PP 43.63

9384 2.5 1164 PP 43.66

9385 2.67 1238 CP 43.78

9386 2.59 1187 CP 43.78 Used for V50 calculation

9387 2.57 1181 PP 43.7 V50 ft/s = 1199

9388 2.58 1238 CP 43.65 Standard Deviation ft/s = 31

9389 2.48 1185 PP 43.88

9407 1.86 966 PP 43.91 Panel 7

9408 1.96 1016 CP 43.61

9409 1.91 1010 CP 43.61 Used for V50 calculation

9410 1.8 946 PP 43.68 V50 ft/s = 991

9411 1.85 981 PP 43.64 Standard Deviation ft/s = 31

9412 1.98 1026 CP 43.66

9413 1.9 980 PP 43.78 Panel 8

9414 1.97 1078 CP 43.98

9415 1.89 1024 CP 43.87

9416 1.8 982 PP 43.86 Used for V50 calculation

9417 1.85 1021 CP 44 V50 ft/s = 1002

9418 1.82 1027 CP 43.93 Standard Deviation ft/s = 24

9419 1.75 980 PP 44.09

9436 2.1 1114 PP 44.01 Panel 9

9437 2.2 1130 CP 44.05

9438 2.15 1113 CP 44.14 Used for V50 calculation

9439 2 1046 PP 44.85 V50 ft/s = 1099

9440 2.07 1106 CP 43.84 Standard Deviation ft/s = 30

9441 1.95 1086 PP 43.68

10650 2 1063 CP 43.7 Panel 10

10651 1.8 1011 PP 43.7

10652 1.9 1048 CP 43.5

10653 1.8 1001 PP 43.9 Used for V50 calculation

10654 1.85 1007 PP 43.5 V50 ft/s = 1025

10655 1.95 1093 CP 43.7 Standard Deviation ft/s = 25

10656 1.9 1022 CP 43.7

10659 1.79 975 CP 44.02 Panel 11

10660 1.4 820 PP 43.92

10661 1.6 883 PP 44.02

10662 1.7 946 CP 44.09 Used for V50 calculation

10663 1.65 887 PP 44.02 V50 ft/s = 917

10664 1.69 932 CP 43.91 Standard Deviation ft/s = 27

10665 1.6 904 PP 44.04

10666 1.4 803 CP 43.96 Panel 12

10667 0.9 622 CP 43.9

10668 0.5 313 PP 44.17

10669 0.7 446 PP 43.96

10670 0.8 587 CP 44 Used for V50 calculation

10671 0.75 497 CP 44 V50 ft/s = 463

10672 0.725 468 CP 44 Standard Deviation ft/s = 25

10673 0.68 442 PP 43.96

Note: Highlighted lines represent those used forV50 calculations.
13

4. Conclusion

Comparing velocity curves for the custom barrel and case to data using standard 

components (Figs. 12 and 13), the custom barrel and case produce increased 

velocity consistency for a given propellant load.

Each panel required a minimum of 6 tests to establish the V50 limit. At most, only

3 additional tests over and above the 6-shot minimum requirement were needed to 

complete each panel. The reduced number of tests required to complete each 

panel further showcase the efficiency and control of this gun and custom case 

combination when testing in this velocity regime. The reduced testing expedited 

the evaluation of this initial batch of composite panels.

When a powder gun is used to test in this low-velocity regime, it requires

consistency and attention to detail during the loading and firing process. Over 500 

tests using this system and testing method have been conducted in support of US 

Army Research Laboratory and customer programs to date.
14

5. References

1. MIL-STD-662F. V50 Ballistic test for armor. Aberdeen Proving Ground 

(MD): Army Research Laboratory (US), Weapons and Materials Research 

Directorate; 1997 Dec 18.

2. MIL-DTL-46593B (MR). Projectile, calibers 0.22, 0.30, 0.50, and 20 mm 

fragment-simulating. Aberdeen Proving Ground (MD): Army Research 

Laboratory (US), Weapons and Materials Research Directorate; 2006 Jul 6.

3. Little D. A low velocity 0.22-caliber gun system. Aberdeen Proving Ground 

(MD): Army Research Laboratory (US); 2009 Aug. 

Report No.: ARL-TN-364. Also available at

http://www.arl.army.mil/www/default.cfm?technical_report=1838. 
15

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