7.62mm, Lethal Limited Range Round For USCG Informational ... · 7.62mm, Lethal Limited Range Round For USCG. Informational Brief for . NDIA 2011. 25 May 2011

7.62mm, Lethal Limited Range Round For USCGInformational Brief for NDIA 201125 May 2011

Project Overview & Objectives

Overview

• JSSAP funded effort for USCG

• 7.62mm Lethal Limited Range Round

• For use in harbor security applications.

Objectives

• Reduced maximum range

• Engage and defeat

Customer Requirements

M80L2R2• Defeat 1/4 inch of mild steel at 200 meters, at a 45-degree angle

• Match trajectory of M80 out to at least 400 meters.

• Capable of defeating soft target out to at least 400 meters.

• Maximum range of 2000 Meters (1500 Meters desirable)

• Capable of being fired from an M14 rifle and M240 Machine Gun

Value to Warfighter

• Operational environment close to civilian populace

• Lethal force often necessary to accomplish missions

• Use of Small Arms at times is restricted due to potential risk to civilians

• Reduced range ammunition will enable USCG to engage targets

Briefing Overview

• Project history

• Added/optimized features and how they were evaluated

• Current projectile design performance

2007

2008

20092010

DESCRIPTION

FY11 Tasks

• One piece • Solid Brass• Cuts along ogive• Standard 7.62 x 51mm Case & Primer• SMP-843 Propellant

• Spark Range Test• Dispersion @ 400m• Radar Test• CFD Study• Updated design• Manufactured projectiles• Charge Establishment • Evaluated Penetration• Entire Cartridge Salt-Fog Test• Radar Test ( w/ & w/o salt-fog exposure)• Analyze & Document Results

Project History

Base

CannelureOgive Cut Depth

Optimized/Added Features that Affect Max Range

V

Flat Base Round Base

Projectile (M80) Base Geometry Computational Fluid Dynamics Study

• Compared aerodynamics of flat base vs. round base M80 • Validated CFD generated static coefficients with spark range data (BRL-MR-1833) • Base shape changes wake vortex formation and pressure distribution

Flat Base Round Base

0.45

0.50

0.55

0.60

0.65

0.70

0.75

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Bas

e P

ress

ure

/ Atm

oshp

eric

Pre

ssur

e

Base Location / Base Radius

Base Pressure Distribution

Round Base

Flat Base

Projectile (M80) Base Geometry and Drag

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.25 0.45 0.65 0.85 1.05 1.25 1.45 1.65 1.85 2.05 2.25

C D

Mach

Spark Range

CFD: Round Base

CFD: Flat Base

Cannelure and Drag

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

0.500

0.000 0.500 1.000 1.500 2.000 2.500 3.000

CD

Mach Number

M80 ball with cannelure

M80 ball without cannelure

Observed Modal Arms Damping at ARL Spark Range Test

λF > 0 and λS > 0 (Shot 32412, Mach 0.74)

•Yaw damps out at muzzle velocity• Yaw increase at Mach .75

(Shot 32421, Mach 2.6)λF < 0 and λS < 0

• 0.27” total thickness• Glass 0.115”• Laminate 0.04”• Glass 0.115”• Meets SAE Z26.1 standards• 50m (2800 ft/s)

L2R2 vs. Automobile Windshield Glass

400m Velocity (1800 ft/s)

L2R2 vs. 20% Ballistic Gelatin

50m Velocity (2800 ft/s)

Entire Cartridge Salt-Fog Humidity Test

0

500

1000

1500

2000

2500

3000

3500

4000

4500

-2000 -1500 -1000 -500 0 500 1000 1500 2000

Rang

e, m

Deflection, m

L2R2

Max Range Impact Area (salt-fog treated/untreated)

L2R2 Impact Area on M80 Safety Fan

Salt-Fog treated rounds travelled farther than untreated rounds

2000m

400m Dispersion Results

-20

-10

0

10

20

30

40

50

0 5 10 15 20 25 30 35 40

y (c

m)

x (cm)

M80

L2R2

ARDEC Design vs. M80 & Contractor Design

Contractor Design

Target = A36 Mild Steel @200m, 45 deg angle

Summary

• Significant yaw growth below Mach 1• Ability to meet distance requirement dependant on

initial QE and projectile ogive cuts being free of debris

• Trajectory similar to that of the M80• Hard target penetration ability not equivalent to that

of the M80• Effective against soft targets and Automobile Glass

Stephen McFarlaneProject EngineerSmall Caliber Munitions DivisionTel#: 973-724-7326Fax#: 973-724-7095stephen.mcfarlane@us.army.mil

BACK UP

400m Velocity (1800 ft/s)

50m Velocity (2800 ft/s)

L2R2 vs. 20% Ballistic Gelatin

Ballistic Gelatin Behind Windshield

Dynamic Stability Relation to Modal Arms Damping

i β

α

PrecessionArm

NutationArm

Stable• Both arms negative (shrinking) or neutral (not growing)

• No yaw• Limit cycle

Unstable• Nutation (fast) arm is positive, precession arm positive (growing)

• Yaw level increases• Tumbling possible

Non-linear Magnus Moment

5th order fit of Magnus moment

Narrow stability bounds

Stability of this round at Mach 0.8 at experimental spin rates is questionable at best