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The Evolution of the M855A15.56mm Enhanced Performance

Round, 19602010LTC Je rey K. Woods

Soldiers from Echo Company, 5th Cavalry Regiment, 172nd Infantry Brigade prepare to clear a stairway during a joint trainingexercise near Bahbahani, Iraq, June 4, 2010. The Soldiers are carrying the M4 Carbine, one of the weapons to which the M855A15.56mm Enhanced Performance Round is tailored. (U.S. Army photo by Kim Smith.)

P erhaps no subject is closer to the hearts of Soldiers than their weaponsand ammunition. For decades, this intense interest in guns and ammohas sparked sharp debate over the best weapons and ammunition on thebattlefield, a debate that continues to the present day. Today, Program ExecutiveOffice Ammunition (PEO Ammo) at Picatinny Arsenal, NJ, manages DODsconventional ammunition programs for all of the military services. PEO Ammohas life-cycle responsibility for the many different types of ammunition used bythe joint warfighter, including general-purpose small-arms ammunition.

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In 1960, when Army Research and Development Newsmagazine the

orerunner o Army AL&T Magazinerst appeared in print, a major contro-

versy was raging over the relative meritso the then-standard 7.62mm roundand a lighter, higher-velocity 5.56mmalternative. The Army adopted the5.56mm M16 rife in 1967; it redthe M193, the rst 5.56mm round.Nevertheless, the controversy continuedover which caliber was better5.56mmvs. 7.62 mmas the magazine notedthrough the years. In 1982, a review by Army Research, Development, and Acquisition Magazine (as it was thencalled) o small-arms ammunitiondevelopment praised the lighter weightand lesser recoil achieved with the

smaller round, yet observed that, Oneo the in eriorities is, however, its pen-etration capability.

In 1982, the Army adopted the5.56mm M855 round to replace theM193 in an e ort to achieve betterper ormance at longer ranges withthe M249 Squad Automatic Weapon(SAW). A steel penetrator in the rontend o the M855 provides increasedhard-target per ormance.

Development o the M16A2 rife, whichmatched the twist o the M249 SAW,also allowed use o the heavier M855round. The M193 is still producedtoday, largely or oreign military sales.

From 2003 to 2006, the Army con-ducted a study o available bullets,commercial and military, and oundnone that provided improved per or-mance over the M855 against the targetsets required o a general-purpose roun

Ensuring Consistency and Environmental Responsibility In post-combat surveys and eld report

rom Iraq and A ghanistan, mostSoldiers have indicated that the round

works ne, delivering the desired e eagainst threat targets. But some Soldiehave reported that the round did notper orm consistently, causing concernin the ammunition community.

In parallel, mounting environmentalconcerns drove the Army to considerreplacing environmentally un riendly materials such as lead. The Armysammunition community, led by PEO

Ammo, saw an opportunity to addressthe two concerns associated with theM855 roundlead and consistency.

Once the M855A1 replaces the leaded M855,it will reduce the amount of lead in production byapproximately 2,000 metric tons yearly, based on

the amount now used to make the M855.

F I G U R E 1 . C O M PA R I S O N C H A R T : M 8 5 5 A N D M 8 5 5 A 1 E P R

Characteristic M855 M855A1 EPR

Cartridge Length 2.248 in No Change

Bullet Weight and Length 62gr No Change

Tip ID Green Bronze from CorrosionProtection

Slug Lead Copper

Cup/Jacket Copper No Change

Penetrator Steel Steel Arrow Head

Corrosion Resistance None Yes

Propellant WC-844 SMP-842

Flash Suppressant No Yes

De-Coppering Agent No Yes

Velocity 3,113 ft/sec Increased

Chamber Pressure M855 Spec Increased

Penetration 3/8" Mild Steel @ 160m 3/8" Mild Steel @ 350m

Soft Target Not Specified Improved Consistencyand Range

M855 M855A1

Steel Penetrator

Copper Jacket (FMJ)

Lead Slug

Propellant

Brass Case

No. 41 Primer

Steel Penetrator

Same Jacket Matebut Reverse Draw

Copper Slug

Different Propella

Same Case

Penetrator

Jacket

Core

Same Primer butwith 4-Prong Stak

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The Armys solution is the new M855A1Enhanced Per ormance Round (EPR).This round o ers better per ormancethan the M855 against all targets likely to be engaged with small arms. This isquite a eat, considering the long-standingsolid per ormance o the M855.

While its true that a number o bullets(such as armor-piercing bullets) canpenetrate hard targets well, they dontprovide the needed e ects againstso t targets. Conversely, some bullets(such as hunting rounds, hollow-point,and other bullets) work well againstso t targets but cant penetrate harderbarriers. Nor do hollow points meetthe Armys requirement to adhere tothe Law o War, de ned as [t]hat parto international law that regulates theconduct o armed hostilities. It is o tencalled the law o armed confict (DoDDirective 2311.01E, DoD Law of War Program). Even today, we have oundno other roundother than the new EPRthat can outper orm the M855as a capable, general-purpose round.

Why the M855A1 ExcelsSo what makes the EPR so good?It uses the same components as theM855a jacket, a penetrator, and ametal slug. But the new round containssome subtle changes (see Figure 1).The copper cup, rom which the jacketis ormed, is reverse-drawn, the oppo-site o how the M855 jacket is drawn.The hardened steel penetrator is almosttwice as heavy as the one used in theM855 and is ully exposed instead o hiding beneath the so ter copper jacket.

The slug is made o copper, makingthe projectile nonhazardous to theenvironment while delivering neededper ormance. Since the EPR issimilar to the M855,the Army canuse the samemanu actur-ing equipment

now used or the M855, providingadditional savings and large-scale manu-

acturing capability. Once the M855A1replaces the leaded M855, it will reducethe amount o lead in production by approximately 2,000 metric tons yearly,based on the amount now used to makethe M855.

There are three main areas in whichthe new round excels: so t-target consis-tency, hard-target penetration, and theextended range at which it maintainsthese per ormance improvements.

This is not to imply that the EPR increases the maximum e ective range o the M4 or M16. Its trajectory matchesthe M855s, which aids in training, less-ens the need to re-zero the weapon, andallows it to link to the current tracerround (the M856) or eventual use inthe M249 SAW. So while the maxi-mum e ective range does not increase,e ectiveness at range does, meaningthe round greatly extends the range o desired e ects along its trajectory.

The Army tackled the consistency issueby ocusing on the yaw o a projectileand how di erences in yaw can in lu-ence results when striking so t targets.The M855 round, similar to the ArmysM80 (7.62mm ball round), is a yaw-dependent bullet. As any bullet travelsalong its trajectory, it wobbles in both

pitch and yaw,causing theprojectile to

strike its targetat di erent attitudes

with virtually every shot.

For a yaw-dependent bullet such asthe M855 or M80, this results invarying per ormance, depending upon

where in the yaw/pitch cycle the bulletstrikes its target. For example, at ahigh angle o yaw, the M855 per ormvery well, trans erring its energy to thtarget in short order. At a low angle oyaw, however, the bullet reacts moreslowly, causing the inconsistent e ecobserved in the ield.

The M855A1 is not yaw-dependent.Like any other bullet, it wobblesalong its trajectory. However, the EPR provides the same e ects when strik-ing its target, regardless o the angleo yaw. This means the EPR providesthe same desired e ects every time,

whether in close combat situations orlonger engagements. In act, the U.S.

Army Research Laboratory (ARL) veriied through live- ire tests against so

targets that, on average, the M855A1surpassed the M80 7.62mm round.The 7.62mm, although a larger caliber,su ers rom the same consistency issas the M855, but to a higher degree.

Hard-target per ormance is a secondarea where the EPR really shines (seeFigure 2 on Page 35). The exposed,heavier, and sharper penetrator, along

with a higher velocity, allows Soldiersto penetrate tougher battle ield bar-riers than is possible with the currentM855. Although its not an armor-piercing round, the EPR can penetrate3/8 inch-thick mild steel at distancesapproaching 400 meters (based on therange at which 50 percent o the roundcan pass through the barrier). TheM855 only penetrates this material outto approximately 160 meters. Not onlyThe M855A1 Enhanced Performance Round offers better performance than the M855 against all targets

likely to be engaged with small arms. (Photo courtesy of PEO Ammo.)

The EPR provides the same effects when striking itstarget, regardless of the angle of yaw. This means the

EPR provides the same desired effects every time, whethin close combat situations or longer engagements.

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is this per ormance much better thanthe M855s with its smaller steel pen-etrator, it is vastly better than the M807.62mm round.

Additionally, the EPR can penetrateconcrete masonry units at ranges outto 80 meters with the M16 and 40meters with the M4. The M855 cantpenetrate this type o battle ield barrierat any range.

Also notable is the EPRs excellentper ormance against so ter intermediatebarriers such as car doors, windshields,or Kevlar abric. The thinner metal

ound on car doors poses no problem. When engaging targets behind wind-shields with the EPR, ARL has shownan increase in the probability o hittingthe occupant, due to both the steel pen-etrator and the copper slug remainingintact through the glass. Furthermore,

ARL tested the round against 24 layerso Kevlar abric out to 1,000 meters,but discontinued the test as the Kevlarshowed no sign o being able to stopthe EPR. The EPR also penetrates some

lesser-quality body armors designed tostop 7.62mm ball rounds.

Another bene it Soldiers will see romthe new round is its e ectiveness whenengaging so t targets at longer ranges.

As a small-caliber projectiles velocity decreases, it eventually will reacha point at which it can no longertrans er most o its energy to its target.Below this velocity, which equates torange, the round is more likely to passthrough its target with little e ect.The M855A1 can maintain consistent,desired e ects at a much lower velocity,resulting in excellent e ectiveness at argreater ranges along its trajectory.

In addition to the above-mentionedper ormance improvements, the EPR is more accurate than the M855.

Accuracy testing during production lotacceptance has shown that, on average,95 percent o the rounds will hit withinan 8 x 8-inch target at 600 meters. Italso uses a lash-reduced propellantoptimized or the M4s shorter barrel.

The good news is that all o theseper ormance improvements come withno weight increase to the Soldier.

Soldiers Are the FocusSoldiers will surely discuss the M855AEPR during their ritual debates onguns and ammo. The new M855A1

will greatly increase Soldier per or-mance on the battle ield, but inevitablSoldiers will have the inal vote as themust maintain their weapon systems,train, aim, and engage their targets.

As always, good marksmanship skillsare critical or success in small-armsengagements. No matter how goodthe bullet, it cant do its job i it doesnhit the target.

During the past 50 years, 5.56mmgeneral-purpose ammunition hasevolved to a level o per ormance thaaddresses all o the major war ightingneeds o our services. The M855A1EPR is a signi icantly improved5.56mm round that provides excellentso t target consistency and vastly bettehard target per ormance, and increaseour Soldiers e ectiveness at extenderanges with better accuracyall

without increasing their load.

The M855A1 represents the most sig-ni icant per ormance leap in small-arammunition in decades. Our Soldiersdeserve the best, and with the M855A1EPR, they get it.

LTC JEFFREY K. WOODS is theProduct Manager or Small-Caliber

Ammunition in the O ce o the ProjeManager Maneuver AmmunitionSystems, PEO Ammo. He holds a B.S.in business administration rom theUniversity o Texas and an M.S. inoperations research rom the FloridaInstitute o Technology. Woods is also graduate o the U.S. Army Commandand General Sta College and De enSystems Management College, and is aU.S. Army Acquisition Corps member

F I G U R E 2 . H A R D TA R G E T P E R F O R M A N C E

Battle BarrierSurrogate (3/8" steel)

Battle BarrierSurrogate (3/8" steel)

Concrete MasonryUnit(M855 won't

penetrate)

Concrete MasonryUnit

(M855 won'tpenetrate)

Results are for M4

Results are for M16

M855M855A1

M855M855A1

M855M855A1

M855

M855A1

(meters) 0 150 300 450

(meters) 0 150 300 450

ARMY AL&T

35 OCTOBER DECEMBER 2010

32_the_evolution_of_the_m855a1_5.56mm_enhanced_performance_round,_1960â2010_201004

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