Why 5.xx mm Cartridges Have Dominated Modern Infantry Weapons and ARDEC Incapacitation Modeling

[Bartholomew Roberts]

In order to understand the origins of the M16 and 5.56, there are two essential pieces of reading:

1. Hitchman’s Operational Requirements for an Infantry Hand Weapon (1952) (also at: http://www.dtic.mil/dtic/tr/fulltext/u2/000346.pdf)
2. Gustafon’s modification of the M1 Carbine to fire a high-velocity .22 cartridge (1953)

While McNamara frequently gets the blame for this, you can see that the roots to the M16 and 5.56 were laid down way before that.

These two studies are important. Hitchman’s study reached the conclusion that even expert veteran rifleman were ineffective as a weapon system past 300yds on average (and much of their effectiveness was lost past 100yds). As a result, Hitchman reached the conclusion that the only way to increase the effectiveness of the individual rifleman was to salvo several rounds to increase hit probability. Gustafon’s study showed a light, high velocity .22 cartridge could perform very well in that range envelope.

From this time forward, you see a lot of effort towards flechette and other small caliber high rate fire weapons (AAI’s ACR 1980 entry, the H&K G11, etc.). This is because if you accept Hitchman’s basic premise about the effectiveness of the rifleman as a weapon system, the only way to increase that effectiveness is shoot more. So at the averaged hit percentage, each magazine contains a certain amount of “stored kills.” By using the smallest (in the logistics sense) ammo available that will do the job, you increase stored kills and the effectiveness of the infantryman.

However, where that line is to be drawn has been a subject of much controversy over the decades. Although the major powers (NATO, Russia, and China) have all chosen some flavor of 5mm. Moreover, advanced sighting mechanisms that allow the enemy to be detected and engaged further away have called into question some of the fundamental conclusions of Hitchman’s work. However, the basic concept of stored kills requires accurately identifying the minimum performance required. If 300yds is no longer the outside limit, then perhaps bigger calibers are necessary.

ARDEC has been busy attempting to develop a computer model that can accurately predict probability of incapacitation of a given ammo type. During the 2017 NDIA conference, they presented their latest research on the subject of terminal ballistics modelling. I thought TFL might enjoy it.

[cslinger]

I think modern and more so future optics’s will change this equation. When I look at that scope system that basically calculates everything for you and essentially fires the correct shot for you all I can think is how game changing that could be when ruggedized and miniaturized.

Look at the ACOG and the drastic increase in head shots it accounted for. (Mostly because that was all the enemy was presenting).

Advanced optics will continue to have a more drastic effect then caliber and may drive caliber to a larger more capable round for further distance.

[Bartholomew Roberts]

I think ARDEC agrees with you, cslinger. I think they are putting so much effort into the incapacitation modeling because as long as they are using the same baseline used in the 1950s for what you want the projectile to do, you’ll never get rid of 5mm, though you may end up with needles instead of bullets.

If you think that is the wrong approach, a more advanced modeling system to demonstrate it is pretty much a must.

[stagpanther]

Pretty cool--combat infantry will now have the capability of ordering up their weapons on a phone ap.

[zukiphile]

Hitchman’s study reached the conclusion that even expert veteran rifleman were ineffective as a weapon system past 300yds on average (and much of their effectiveness was lost past 100yds). As a result, Hitchman reached the conclusion that the only way to increase the effectiveness of the individual rifleman was to salvo several rounds to increase hit probability.

Emphasis added.

Is that conclusion plausible? One of the AK100 series incorporates a two shot burst feature so quick that it sound like a single shot based on this reasoning of increased hit probability.

When I am shooting paper, it may take more than one shot to land in the x-ring, but a higher rate of fire doesn't itself seem to increase the odds that I will hit the x-ring. If I am missing with a single shot, are several more shots influenced by recoil a remedy?

[Bartholomew Roberts]

I’ve summarized quite a bit. Hitchman’s work is more extensive and defines an acceptable dispersion and explains how it increases hit probability. Of course, it was also conducted using M1 Garand iron sights vs. say, an ACOG.

[jmr40]

Exact numbers are impossible, and even accurate estimates can be argued. But the "estimates" I've seen say that in WW-2 our soldiers fired about 20,000 rounds for every hit on an enemy soldier. By Vietnam that number is 50,000 and in the Middle Eastern wars I'm seeing 250,000 rounds/hit as an estimate.

The exact numbers can be debated, but suffice it to say there have been a lot of shots fired/hit and having a lot of ammo available will probably save a lot more lives than fewer, but more powerful rounds.

This isn't really a reflection of poor accuracy as much as tactics. Rifle fire, even during WW-2 was used to force the enemy to keep their heads down and remain in a static position until artillery, tanks or air strikes could take them out. Or for other troops to advance close enough without being fired on.

Carefully aimed rifle fire at ranges over 50 yards just haven't happened very often in the last 100 years. There are times where the 223/5.56 does come up short. But I've said for a long time that had we stayed with the 308 as our main battle rifle we'd have filled a lot more body bags over the last 50 years. I think the idea of having a few rifles in each squad capable of longer range work is a move in the right direction, but I don't think every soldier would benefit from that.

[2damnold4this]

Thanks for posting, Bart. I looked at the last link and I don't really understand it but I'll check out the others and take another look at the last one.

[FrankenMauser]

I’ve summarized quite a bit. Hitchman’s work is more extensive and defines an acceptable dispersion and explains how it increases hit probability. Of course, it was also conducted using M1 Garand iron sights vs. say, an ACOG.

Interesting.
-And likely far more applicable today, than prior to Vietnam.

Does Hitchman hit, at all, on the fact that most rifleman never actually fired with an intent to hit the enemy? At best, the average rifleman fired over the enemy's head. More often than not, they faked it or didn't fire at all.

I don't have my copy handy in order to cite specific statistics at the moment, but the subject is discussed quite a bit in "On Killing", by Dave Grosman.
I'm probably wrong, but I believe the 20th century average, prior to Vietnam, was less than 18% -- that is, less than 18% of soldiers (whose job it is to be shooting the enemy) firing with the intent to hit the enemy, while the rest hide, run away, fake the act, hold the rifle without firing, or intentionally shoot well over the heads of the enemy.

As Grosman discusses in his book, that very issue is how we end up with battles like Rorke's Drift. At point blank range, volley after volley was fired by the Brits into the Zulus. Yet the hit rate was estimated to be less than 8%.

I do have a quote by a U.S. Marine medic in Vietnam, from Grosman's book:
"One of the things that amazed me is how many bullets can be fired during a firefight without anyone getting hurt." - Douglas Graham.

[He is referring to the lack of effectiveness and precision of the fire - not a weapon system inadequacy.]

[marine6680]

Optics do help increase effective range.

The question is how much...


On a static range, a 4x scope makes hits on a torso Target at 500yds easier for most shooters. Even shooters who do poorly at that range can see an improvement.

But how do you gain that improvement?

For competent shooters, the magnification will increase their confidence and allow for faster hits.

For poor shooters, they are likely to see their aiming errors and correct for them, making better hits, at the expense of some speed.


The next question is... Does that translate into a combat environment.

If your shooters are in a stable position with good cover, and are scanning for targets... Yes, you will see increased effective range. But this is the closest to a static range you are likely to see on a battlefield.

If they are actively engaging targets in a more dynamic environment... Be it maneuver tactics or are being actively engaged by the enemy, it is not likely that they will be able to bring to bear their full potential.


So, I think you will see the 100yd drop off extend to 200yds on average... And the max effective move from 300yds to 400-500yds... With increased range for the drop-off when the situation is more stable.

This is my educated hypothesis, based on my experience as a shooter through the years, and during my admittedly limited combat and maneuver training.


Until we can eliminate the human induced errors, in improper aiming and range estimation, and especially the error induced simply because a human is holding the weapon and can't be completely immobile/still... We will not see much improvement in effective range. Good BDC and range estimating reticles help, but you still have a squishy user pulling the trigger.


This is one reason I was thinking if something like 244 valk would be a useful military caliber. Juiced up a bit like 5.56 is over 223, and running 80gr bullets, seems like it would push the effective range, of the bullet at least, out a couple hundred yards over 5.56.

Basically a heavier bullet with close to the same MV as current 62gr. (Due to the increased powder capacity of 24 valk) But I am not sure if you could push the caliber to that level. Just speculation ATM.


As far as the intent to kill question... I believe that was taken to heart and modern training is done in a manner to help reduce the number of guys who do not aim to kill.

[Mike Irwin]

It took a LONG time, and a lot of effort, to get military people away from the long-held and cherished position that the American soldier was, at heart, a long-range sniping machine.

The studies that were done after World Wars 1 and 2, both in the US and in Europe, all pointed to the standard military cartridges of the time being overly powerful.

No one was planning on a conflict in areas where engagements beyond the effective range of the 5.56 would become fairly common place.

It also hasn't helped that the military's choices for alterations to the standard rifle have decreased effective range even more.

You can't lop 6 inches off the barrel and change the twist from 1-12 to 1-7 (making the bullet a lot more stable and less prone to tumble) and expect to maintain the same effective range.

The short-term answer has been the role of the designated marksman with the 7.62 rifle.

What baffles me, however, is the military's extreme reluctance to adopt a more thoroughly integrated 5.56/7.62 equipment structure for the troops. One of the major concerns has always been one of supply, but truth of the matter is that the one thing the US military has been pretty darned good at for a long time is supply. And it would provide a much more effective combat stance.

[Bartholomew Roberts]

Does Hitchman hit, at all, on the fact that most rifleman never actually fired with an intent to hit the enemy?

Grossman relies heavily on S. L. A. Marshall’s work for that, which is not uncontroversial. Marshall is a contemporary of Hitchman and while I believe some of Hitchman’s range data at which combat occurred is likely derived from Marshall’s interviews, the actual hit percentages were done in research with various rifleman from expert qualified combat veterans with WW2 and Korea experience to novices shooting various controlled scenarios.

The link above explains the process in great detail and is a good read in its own right.

[stagpanther]

Please 'splain to me--since I'm not the sharpest pencil in the box--why this supposed scientific analysis of projectile effectivemess is muddied by the introduction of shooter's and accessories variables? I think it's pretty darn hard to figure out and predict the projectile performance alone without bringing in "outside the cartridge" variables into the calculus.

[Bartholomew Roberts]

No one was planning on a conflict in areas where engagements beyond the effective range of the 5.56 would become fairly common place.

The latest fantasy research project I’ve read about wants to defeat level 4 plate at 600m and proposes an infantry rifle launching a 125gr projectile in the 6.5-7mm range at 3,500fps from a 16” barrel. I’m not sure how they intend to overcome the technical difficulties around that goal; but if they hit it, that will sure remove any questions about the effectiveness of the standard infantry rifle.

[stagpanther]

125gr projectile in the 6.5-7mm range at 3,500fps from a 16” barrel. I’m not sure how they intend to overcome the technical difficulties around that goal;

Only one way I can think of--and that's IMR FairyDust 5000 powder has been developed.

[Jim Watson]

The studies that were done after World Wars 1 and 2, both in the US and in Europe, all pointed to the standard military cartridges of the time being overly powerful.

It took a while to sink in. The Italians and Japanese went to INCREASED power infantry rifles after they were already in combat. The Italian effort flopped, but the Japanese were issuing 6.5s and the later 7.7s right along.

[Bartholomew Roberts]

Please 'splain to me--since I'm not the sharpest pencil in the box--why this supposed scientific analysis of projectile effectivemess is muddied by the introduction of shooter's and accessories variables?

A key part of Hitchman’s analysis is that infantry combat rarely occurs past 300yds because terrain makes it difficult to detect enemy combatants at that range. Another part of his analysis is that even expert qualified combat veterans rarely make hits at 300yds, and their efficiency drops off markedly after 100yds - thus the best way to increase hit probability is to shoot more.

If those two statements are true, then carrying a 7.62x63 or 7.62x51 is just wasted weight and less effective infantry since on average only a low percentage of rounds will hit past 100yds. If either of those statements aren’t true, then all the conclusions that follow then have to be reexamined as well. If adding an ACOG increases the hit percentage out to 400m, then ideally you want the most compact catridge that can still deliver incapacitatiom at 400m. If a ranged optic or improved training increases hit percentage better than a low-recoiling Project SALVO type needlegun, then maybe the emphasis on small, low-recoil cartridges needs to be reexamined

At the time Hitchman did this study, “body armor” was a steel helmet, everyone used iron sights and weapons based NODS were very primitive. Scopes and NODS change ranges the enemy is detected and likely increase the distance they can be engaged. Body armor changes the minimum performance required (along with better understanding of terminal ballistics) and now that minimum performance may need to be delivered at increased ranges as well.


To ridiculously oversimplify this, let’s use a wargaming analogy. Your elite, combat veteran units will hit at 3% at 300yds. So for each 100 rounds he fires, that is three hits on an enemy soldier at 300yds. If you change his ammo to something primarily geared to under 300yds, you can triple the amount of ammo he can carry. If a lot of your warfighting strategy is based on simple computer models, you can see where this leads directly.

[marine6680]

Stag...

Well... Caliber effectiveness from a purely analytical and scientific standpoint does not count in human and equipment variables.

That's well and good to know the effectiveness potential of the round in question. You know what the caliber can do on it's merits alone... It is important information.

But you can't remove the human and equipment variables when discussing actual combat effectiveness.

A bullet doesn't do much if it doesn't hit the target.

So combat effectiveness must take in account the potential of the round itself, combined with the effectiveness of the soldier at deploying the weapon system that uses said round, under combat conditions. It's all linked.


Example... A caliber like 7.62x51 is a very effective round, out to distances any reasonable shooter could be expected to hit a torso target, and can be effectivly fired from a shoulder fired rifle...

But, when you start factoring in other variables, such as typical engagement distances, actual combat effective range of an individual soldier, ammo weight... Etc... You find that on the end, that round is beyond what most soldiers need. It's capabilities exceed that of the average soldier.

That means there is inefficiency and waste.

So see where you can trim off excess and gain in other areas.

Which lead to the current 5.56... At it's inception, it was effective at typical engagement distances and within the average soldier's combat effective range. It was lighter in weight and smaller in size, which allowed for a larger round count for the same weight load. Recoil was reduced allowing for easier shooting and faster aimed follow up shooting. The rifles that fired it are lighter than ones firing older more powerful calibers.

Changes to the weapon platform have altered things as well.

A change in twist reduced the tumbling effect when the bullet hit tissue, and then the move to a different bullet design reduced it further... Reduced barrel length reduced velocity and max effective range.

So in the end, you can't remove all the other factors when discussing actual real life effectiveness.

[Bartholomew Roberts]

A change in twist reduced the tumbling effect when the bullet hit tissue.

This is a pernicious myth. Tumbling of FMJ spitzer bullets depends on the angle of attack at the moment the bullet hits the target, which is essentially impossible to control. You can’t spin a bullet fast enough to spin-stabilize it in human tissue.

[johnwilliamson062]

As indicated above, it seems only about ten percent of soldiers actually aim at the enemy. Some will aim around them to suppress, many either won't fire or won't fire anywhere close. And from my memory those numbers are for infantrymen specifically and exclude the 50% + members of the military in a support role. I can't remember the study and I know it was dated when I read it a decade ago. Maybe post WWII.
The US fired THOUSANDS of rounds for each kill with a rifle in Vietnam. I imagine that number hasn't improved.

Find the ten percent or less of soldiers who are actually aiming at the enemy, figure out what their proficiency is, and give them the weapon that matches their skills the best. IF they can shoot make them a designated marksman. If they can sort of shoot give them an AR with upgraded optics. If they can't shoot give them a SAW, grenade launcher, or similar.

Give everyone else noise makers of whatever style you prefer. A full auto 22LR with three times the ammo will do just as much if they are aiming away from the enemy. Maybe the drop will put those bullets fired over head on target.

[rickyrick]

Most soldiers can’t shoot very well, even when they are trying to qualify.

[zukiphile]

Originally Posted by JW62

Give everyone else noise makers of whatever style you prefer. A full auto 22LR with three times the ammo will do just as much if they are aiming away from the enemy. Maybe the drop will put those bullets fired over head on target.

Plus, think of the opportunity to purchase surplus 22lr.

[stagpanther]

I'm not arguing the importance of the "usability" of the platform--nor the overwhelming importance of the user as part of the overall equation.

What I see is a pretty general consensus that an upgrade of some kind is needed due to real or perceived ballistic shortcomings of existing cartridges. That can of course spin off into all kinds of discussions related to personal/logistics efficiencies--but what I'm trying to get at--and what the software mentioned above seems to try accomplish--is providing at least some direction in a new ballistics package to try to address those short-comings.

The more I read the stuff above the bigger the impression is to me that basically the message is until operator effectiveness, training and tactics are improved--there's not much use in developing a new carbine or medium weight rifle cartridge for troops. Let's say a new quick acquire self ranging optic is distributed (already in use?) and the weapon is lightly balanced with vastly reduced recoil, muzzle-flip etc. Does it necessarily follow that kill rate will automatically climb? I would think yes--but I have no knowledge of battle conditions so that's may or may not be a correct assumption.

Forgive my armchair point-of-view interest--but I am interested.

[2damnold4this]

What are they measuring in the last page of the third link? If it's tissue damage, I would think the shotgun would do more damage at close range than rifles firing intermediate cartridges.

[Mike Irwin]

"The Italians and Japanese went to INCREASED power infantry rifles after they were already in combat."

The Italians actually didn't. They adopted the 7.35 in 1938 based on their experiences in Africa in the 1920s and early 1930s.

They were forced to withdraw the 7.35 after their entry into World War II because they didn't have the capability to rearm their troops wholesale, and didn't have the logistical capabilities to supply both types of ammunition to their troops.

In both cases, the primary concern was with adequate performance at longer distances. Much of that was the simple fact that the bullets would penetrate through and through most targets before they had a chance to do any sort of significant damage.

The Italians did design a pretty effective bullet for the 7.35 that tumbled a lot more quickly no matter what velocity it met the target at.