Criticizing the M855 5.56mm Round

1-23 Infantry Regiment, 2nd Infantry Division, pulls security, armed with a Colt 5.56 mm M4 carbine rifle

US uses bullets ill-suited for new ways of war

The smaller, steel-penetrating M855 rounds continue to be a weak spot in the American arsenal. They are not lethal enough to bring down an enemy decisively, and that puts troops at risk, according to Associated Press interviews.

Designed decades ago to puncture a Soviet soldier’s helmet hundreds of yards away, the M855 rounds are being used for very different targets in Iraq and Afghanistan. Much of today’s fighting takes place in close quarters; narrow streets, stairways and rooftops are today’s battlefield. Legions of armor-clad Russians marching through the Fulda Gap in Germany have given way to insurgents and terrorists who hit and run.

Fired at short range, the M855 round is prone to pass through a body like a needle through fabric. That does not mean being shot is a pain-free experience. But unless the bullet strikes a vital organ or the spine, the adrenaline-fueled enemy may have the strength to keep on fighting and even live to fight another day.

This, of course, is nothing new. And though there doesn’t seem to be much doubt that the 5.56 is far from perfect, it’s also hard to argue with the results our troops have had with it. Even with the majority of our troops now using M4 carbines with shorter barrels than M16 rifles.

All that said, I still wonder if a .45 caliber submachine gun might not be in order for many of our troops in the current battle zones. Not for infantry, maybe, but wouldn’t most non-infantry be better off with something like TDI’s KRISS submachine gun? I don’t think anyone is arguing against the effectiveness of the .45 ACP against unarmored targets.

Seems that it would make sense in a mostly urban environment as a personal defense weapon. I’d think it would be much more effective than either a 9mm pistol or an M4 carbine. I posted on the PDW issue a year ago.

To my knowledge, nothing ever came of the reported interest the US Army had for ‘a compact, medium-powered firearm for issue to vehicle crews.’

UPDATE: More at Danger Room.


  1. I have some sad news. I talked to a friend who works in the Pentagon the weekend before last. I had emailed him that article regarding the testing done between the M4 and several other rifles in the sandy conditions. His take on the test was that it didn’t mean anything. His, and I assume the Army’s postion is that the M4 is the right weapon in the right caliber, period. I would have never spotted this guy for a party line sort, but I’m guessing his politics and his dad’s are light years apart. He kept telling me that what the US Army really needs is more money. At least 4% of GDP. When I told him we were already spending at or above Cold War levels in inflation adjusted dollars he said it made no difference. Anything less than 4% of GDP would put our forces in decline. I’ll tell you, there’s light years difference between what we talk about in the trenches at the aerospace companies and what’s accepted fact in DC. A .45 cal is a step in the right direction, but there are two parts to the equation when discussing the lethality of a small projectile. Diameter is important, but if the bullet is going slow even a large diameter projectile won’t do much damage. That’s because in a low expansion projectile it is the shockwave that does most of the damage. If the projectile is big but slow that equals a weak shockwave. If it is small but fast the shockwave is still weak. What you want is a large diameter bullet at high speed. That’s what does the big damage, because it drags a big shockwave through the body. That shockwave causes cellular structures to explode many diameters from the impact site. The problem is, we are letting ‘humanitarians’ (spelled L-I-B-E-R-A-L-S) determine what kind of weapons our guys can have. For many years lethality was purely the measure of the weapon. Around WW2, firing rate began factoring into the equation, which is why our guys started using semi-automatic weapons. They were a good trade off between a high rate of fire and lethality. Today we have gone backwards. You have to hit an enemy with a fully automatic burst to have any effect. That’s crazy. There’s no economy to having to hit someone more than once to bring them down. Instead of exploring new technologies to keep firing rate up while providing ever more powerful projectiles, we have gone to these wussy guns that don’t kick hard enough to give your balls a good scratching.

  2. One thing to remember is that the move to lighter bullets were influenced by studies of WWII that showed most bullets missed. A missing bullet should be as small as possible, a hitting bullet should of course be as large as possible. The change from a drafted to volunteer army has probably means that we should have changed the arms used at the same time. Our army is more effective on a per solider basis than it was i the past and is hitting more often.

  3. Before bashing the 5.56mm, I would love to see comparitive tests between the M885, Mk262 (that Sierra 77 grains) and the Barnes Triple Shock (70 grains all copper). Im sure that the Mk262 since its 24% heavier at the same time its more fragile.

  4. Correction: Im sure that the Mk262 would perform much better since its 24% heavier than the M885 at the same time its more fragile.

  5. On lightly clothed / no body armor targets, the old 49-grain, higher velocity rounds would probably be more effective with their tendancy to tumble. It has become obvious that our soldiers and Marines will be saddled with the POS M16/4 for decades to come.

  6. If most bullets miss, as you would expect under combat conditions, then requiring 2 hits to cause serious injury is a tragic misinterpretation of data. The .308 round seems like a good next step after the 30-06 since it is smaller and lighter yet packs about the same punch. The discontinuity comes with the .22. There was no data or experience base upon which to make that choice. It was simply an attempt to make war more ‘humane’. It was quasi-non-lethal. It followed the Vietnam war philosophy that our troops were expendable for political ends. This is ironic in light of the Army’s recent recruiting slogan, ‘An Army of One’. If that was really their philosophy, they’d continue to develop more powerful weapons for our soldiers, not less. They would not require the individual soldier to call in an air strike (if an airplane is available) or an artillery strike (if artillery is available) to deal with an enemy. That’s a sacrificial approach to infantry. To ease their consciences, they provide body armor. Infantry is really supposed to be nothing but a sensor device for the all important, mega-dollar glory weapons.

  7. I bet they had a similar discussion in the early 1900s when they went from the .38 to the 45 as the official sidearm for the military.

  8. Well, Im a big fan of the 6.5 Grendel.After 1100 yards it can conservates more energy than a 9mm at point blank range! I know americans has some kind of irrational fear towards bullpup designs, but I believe that 5.56mm benefits a lot from it.

  9. A 6.5mm is a respectable bullet, but the question is not only how much energy does it keep. You also have to consider how much energy it transmits into the target. Another thing to consider is the fact that you can shoot a 6.5mm bullet out of an 8mm barrel using a sabot. The converse is not true. An 8x57mm will shoot a 6.5mm bullet with a sabot faster than a 6.5x57mm cartridge will.

  10. A return to a reliable, effective close support weapon is long overdue, and one need only look to the M3 ‘Grease Gun’ to find a heavy hitting weapon. It used standard .45 ACP rounds, which are known by all who own a 1911 to be effective, hard hitting rounds. Its easy and cheap to produce, much smaller than the M4 Carbine, so tankers finally get what they need, and most important, its been proven recently with the military. Thats right, as recently as 1991, it was deployed with the 19th Engineer Battalion, attached to the 1st Armored Division in the first Gulf War. This constant cry for ‘newer, sexier’ arms is out of control. Why waste funds on development of a weapon that will end up unable to match the performance of a simple, light weapon effective out to 100 yards (which, if you think about it, is more than enough in house- to house-combat), which can fire at approx. 400 rounds a minute, with a greatly reduced chance of blowing through not just the wall of the room you’re in, but the walls of the NEXT house. And a weapon that has proven itself for over 66 years. K.I.S.S. (Keep It Stupidly Simple) should be tattooed on the head of every congressman who serves on a weapons funding board.

  11. Dfens, according to my rough calculations, the 6.5 MPC round at 95 grains, out of a 14.5′ barrel deliver more energy than the 7.62X39 mm round, fired by an AK47. It also has a better BC than the 5.56 mm, 7.62X39 mm, and 6.8 SPC rounds. It is almost as good as the 6.5 Grendel has, which means that can deliver the punch very well at short or long range. Meanwhile, the 6.5 MPC is weighing only 10% more than the 5.56 mm cartridge and requires only a barrel and bolt change to be used with the current M16/M4 rifles. The 6.5 Grendel and 6.8 SPC are good cartridges also, but their performance is coming with the price of 30% weight increase and requirement for significant changes to the rifle and magazines.

  12. I don’t think you’re following me, Delphi. The amount of destructive energy a bullet causes to the enemy is relative to the size of the shockwave it drags through the tissue. Now I’m assuming the bullet is not hitting a bone here, because obviously that will change things considerably. The .223 is slipping through without causing an appreciable amount of damage because even though it travels at high speed, it doesn’t displace much tissue in it’s path through the body. Now a .256 diameter bullet does displace more tissue, but not a lot more. It’s a step in the right direction. Maybe, given the modest weight of the cartridge and the low kick produce, maybe it is an optimum round. That wouldn’t be my guess, though. I tend to prefer .30 cal or larger, and I don’t see a down side to guessing too big, because like I’ve said, you can always shoot a smaller bullet out of a bigger bore, but the converse is not true. In fact, there’s a lot more you can do with a bigger barrel. You can shoot all sorts of specialty ammunition, like fin stabilized flechetts, they’re better for lobbing those grenades-on-a-stick things we used to use in WW2, they’re lighter for the same stiffness as a smaller bore barrel, they’re easier to clean. As Murdoc and others have noted, the .45 ACP round has performed really well at short range in a number of weapons. I don’t see why the Army doesn’t develop a whole range of guns based on a .45 cal bore. They could have everything from a belted magunm to a pistol based on that bore, and they could launch a huge variety of projectiles from them. Of course, that would require an Army of thinkers, instead of an Army of yes men.

  13. In regards to Dfens original comment…………that’s the party line all right, that attitude has been widely discussed in the defense and gun media. The key question, that I’ve never seen answered, is WHY the Army establishment is so stuck on defending the M4/5.56 M855 combination? Can you give us any insight into that? A side bar to this issue is that of all the police (current & former) I’ve talked with about the 5.56 are quite to very satisfied with it. HHHHHMMMMM???? The troops are bitchin’ (and rightly so) about it and the cops are sayin’ it’s cool. What’s Up With That? That’s easy enough……….bullet design. The rifles are the same (M4/14.5 in barrel) but the bullets fired are different. The troops are using a semi armor piercing round designed to perform well against Warsaw Pact soft body armor and steel helmets at 200m, while the cops are able to use hollow point, ballistic nylon tipped, and other types of bullets. Most of which tend to destabilise and tumble and/or expand upon hitting the target (intended hopefully!). Thereby imparting that all important fight stopping energy (as noted by other posters above). Seems to me, what we really need isn’t another change in calibers, just a redesign of the standard 5.56 bullet to something that’s more effective at energy transfer and conforms to the Geneva Convention (or any other agreements the US is a signatory of). I’m not taking anything away from the validity of the comments above about the 6.5 and 6.8 mm rounds. They’re unquestionably more effective cartridges, because they’re more powerful rounds firing heavier bullets. Adopting any of them is obviated by the US dragooning the rest of NATO and the West into adopting ‘our’ 5.56 round as the standard though. What would my personal pick be for when I go back to the Stan or to Iraq (supposing supply wasn’t an issue)? Either the Masada or a Barret with a 16in barrel using the 6.8mm SPC.

  14. HOrnady makes a 62 grain ball bullet of construction identical to the older M193 round, in that it is not intended to be a body armor or armorpiercing round, and its terminal performance is like that of the M193 in that it goes in about 2-3 inches and then loses its directional stability. The M855 round does do this, but it needs to penetrate over 10 inches to do so, and the average human is only about 9 inches deep from front to back. The contract for ammo needs to be changed to the Hornady 62 grain conventional constructed bullet. Then when we go up against someone without all the fancy crap on them, we can kill them better. And the ammo would cost less as well, something for the beancounters out there.

  15. I wish I knew the answer to the ‘why’ question too, Flanker. I think part of the answer is that the Army set up a bureaucracy whose sole purpose was to be an apologist for the M-16 and that bureaucracy doesn’t want to die. At least, that’s how things usually work in my part of the military-industrial complex. As far as bullet tumbling goes as a method of causing more tissue damage, this typically doesn’t seem to work. If a bullet is that close to instability, it will wobble significantly in flight and can easily be deflected by leaves and small branches. Even though I’m not real hot on the 6.8, I did find an article that others might enjoy regarding its development and merits.

  16. Good points by USMC Steve that I did not mention! If it’s not going to expand, it’s got to tumble and early enough to impart damage via energy dump. It’s not only bullet design, but weight bias and rifling twist. Police agencies are not only free to pick their bullet design, but their rifles twist as well………..I suspect most have wisely avoided the Mil Spec 1:7 rifling that over stabilises the M855 (and it’s cousins) round. My wish list Masada or piston operated Barret would have the twist recommended by their guys……….that works best with the 6.8mm bullet. Dfens, sounds like my old State of Michigan Criminal Justice/Law Enforcement agency (entrenched Civil Service—pronounced Serv Us LOL!). Once someone (bureau, department, division……..pick one) becomes invested in an idea, concept, design, or whatever…..they’ve got enough of their political capital and/or reputations in it; that to later deviate from the party line, or even worse………to reverse course is saying ‘I’m/we were wrong’ and the the others were right. Thereby losing authority, respect, power and worse……maybe budget.

  17. No horse is ever so dead it can’t stand a bit more beating. The Army spent several years investigating this particular problem after complaints came out of Afghanistan in 2002 — and came to some rigorous science-based conclusions. The study took a hard look at both 5.56mm (not just M855, either) and 7.62 (and dabbled in a range of other calibers). There’s a summary article on the effort available as a free download – go to and download the WSTIAC Quarterly newsletter. It’s the lead article: ‘Small Caliber Lethality’. Reading between the lines of the conclusion, it would appear (1) work is continuing, and (2) lessons learned are being applied in some fashion.

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