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

[Mike Irwin]

"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."

Actually, it's not.

Many factors come into play -- bullet weight and length and spin all play critical factors in when and how much a bullet will tumble when it impacts a target.

But, the higher the ballistic coefficient, the more resistant a bullet will be to tumbling. That's why the Japanese and Italians wanted to drop the their 6.5 mm rounds, yet it's why WMD Bell often chose the FMJ military 6.5mm ammunition for elephant culling. The bullets would often penetrate 2 feet or more into an elephant's skull before showing any signs of tumbling.

In the case of the 5.56, however, it's not so much that the bullet tumbles, it's that the bullet tends to break into two or three pieces above a threshold velocity (IIRC about 2,500 fps.)

This page (it's in Danish, I believe) has some very good graphical representations of how deeply some FMJ bullets will penetrate before they begin to tumble starting in post 6.

http://www.milforum.net/showthread.p...reffer-kroppen

The first one shows just how deeply a standard 6.5x52 Carcano bullet will penetrate before beginning to tumble. Given the average human torso's 25 cm thickness, you'd need to line up 2 to 3 people before you'd get any sort of tumbling.

[RC20]

Missing from the discussion is that since WWI (and depending on the conflict prior) most miltaries wee made up of conscripts (Boors aside and they truly were longer range capable)

GB had a professional core as did the US et all (or sorts) but when push came to shove, massive conscripts were used.

What has changed is the all volunteer force for the US, more back to the cohesive forces of much longer ago combats.

And not to denigrate the conscription (or volunteers, my dad was one of those) they were not professional soldiers and thrown into combat with a minimum of training. Some became very good, some performed as poorly as any of us thrown into combat and many somewhere in between.

WWI on it was massive fire power be it machine guns or artillery.

WWII saw the Germans with the stunningly fast firing MG34 and MG42.

Realistically the US went from a round that was far too long ranged (06 or 7.62) to one that was too short ranged by foolish decision.

Being so called out ranged goes back to Cuba when in fact most of them wold not have done any better with the Mauser's the Spanish had than the Kraigs the US had.

USSR went with short ranged round after WWII, but they also fought WWII with a lot of sub machine guns and massive casualties were a given.

Technology has changed throughout, more weapons and more precision as well as the all important ability to control the support weapons and the communications to go with that.

And keep in mind, we have always "poked" holes in people as the Army insists on a penetrating bullet rather than one that is oriented to the combat situation being faced at any given time.

If you are going to poke holes thorough people the caliber does not make a great deal if any difference, range does.

2500 yards is too much for most, M4 is shockingly short ranged (as noted about cutting barrel down form 20 inches and changing the twist)

Mixed ammo was delivered in all wars and WWII from Carbine to 45 acp and 30-065 as well as 50 caliber.

Something capable out to 1000 yards in the right hands (and sights to use that) and something good to a solids 600 for the rest.

And bullets that suit the need would be far more lethal.

[T. O'Heir]

First link is dead.
However, the only reason the U.S. Army and subsequently the rest of NATO got the M16 and 5.56 jammed down their throats is because of McNamara. Playing with the Carbine and Hitchman’s study(whoever he was) had nothing whatever to do with it. McNamara thought the M-16 was sexy.
Every other NATO country was busy working on a cartridge suitable for European battle fields. Where typical engagements during W.W. II were at roughly 300 yards and nothing to do with Hitchman.
Said cartridges were mostly 7mm's like the .280 Enfield/British. None of which were selected as the head of the US Small Arms Bureau of Ordnance, one Colonel Renée Studler, was vehemently an NIH kind of guy. Not Invented Here, as in The U.S. of A, means its no good according to Studler. Who falsified documents and lied about it to get the 7.62 x 51 adopted.
"...Most soldiers can’t shoot very well..." If they shoot at all.
"...The US fired THOUSANDS of rounds for each kill..." That's thousands of rounds of all types. Not just rifle fire. Something on the order of 50,000 plus of everything from rifles to 8" guns per kill. I think it included bombs and naval gun fire too.

[Bartholomew Roberts]

Many factors come into play -- bullet weight and length and spin all play critical factors in when and how much a bullet will tumble when it impacts a target.

Mike, none of examples you offer demonstrate what I am referring to.

You can understabilize a bullet to the point it keyholes (a la M855 in a 1:12 barrel), but you cannot stop a spitzer bullet from tumbling by increasing the rate of twist. Spinning a bullet fast enough to keep the heavier rear from wanting to swing around would require a twist rate never seen on any firearm.

When 55gr 5.56 FMJ is fired out of a barrel (whether 1:14, 1:12, 1:9, 1:7)*, it’s tip wobbles through air like a spinning football from about a 2 degree angle of attack to a 0 degree angle. If it is at 2 degrees when it hits, it upsets faster than if it is at zero degrees when it hits; but this wobble is present regardless of twist. The wobble** is also more pronounced for the first 50m of bullet flight.

*The U.S. Army’s Wound Ballistics Research Lab has conducted this test and found zero difference in terminal ballistics due to twist.

**Here is an Army Research Lab study demonstrating how they measured this “wobble” on bullets in flight. They can even predict at what distances the test rifle would have maximum terminal effect (see pgs. 14-15): https://docs.google.com/viewer?url=h...u2/a458409.pdf

[Mike Irwin]

"but you cannot stop a spitzer bullet from tumbling by increasing the rate of twist. Spinning a bullet fast enough to keep the heavier rear from wanting to swing around would require a twist rate never seen on any firearm."

Bart,

No one is saying anything (or if they have, I missed it) about spitzers not tumbling. It's how far they will penetrate before they tumble.

You can certainly slow down the point at which a bullet begins to tumble by increasing its stability through it's spin rate. Or by pushing weight to the rear of the bullet (as is the case with the Russian 5.45 design).

However, there's an upper and lower limit at which that can be done. Exceed either the upper or lower limit and the bullet will tumble faster. Or, in the case of a number of modern bullet designs, over stabilizing a bullet can increase its potential for breaking up in the target.

Again, there's a limit to that, as well.

I believe that was at least part of the reason for adopting the faster twist in the M4. Velocity was lost with the shorter bullet, but the faster spin would (supposedly) make up for the lower velocity by making it more prone to breaking up on impact.

[marine6680]

^^ Basically that is what I was saying.

Tumbling isn't eliminated, but delayed. In 5.56, the initial yaw from starting to tumble causes the bullet to break apart and fragment.

Delaying the point that happens, affects the performance.


As it stands, I think a round that is very effective inside 400yds, being that it breaks up or tumbles easily in that range, and remains mostly viable out to 600yds... That is probably the most you would ever need from a general purpose infantry round.

600yds is pushing it for the average soldier in combat conditions to make hits, and more than likely those hits are from a consequence of volume of fire and probabilities than aimed intent.

The only real reason for needing 600yd viability is for theaters of operations that have open terrain and even hill to hill engagements.

Ideally, you would employ maneuver doctrine and use suppression to allow for a group to close with the enemy and engage from a closer and more optimal position. Moving to inside the more effective range of the round.


If you want longer range shots, those are going to be more one off and special case than general combat, so one guy on a team with a rifle able to reach out to 600yds or a bit more, with more authority, is likely enough.

[johnwilliamson062]

"Ideally, you would employ maneuver doctrine and use suppression to allow for a group to close with the enemy and engage from a closer and more optimal position."
Just as artillery and mgs took over from WWI, I think drones are soon to take over the long range fighting. Before long I suspect transports will surrender their turrets for drone docks. I suspect the next transition will be to even shorter range weapons designed primarily to defend a position on the brink of being over run.


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[Bartholomew Roberts]

Originally Posted by Mike Irwin

You can certainly slow down the point at which a bullet begins to tumble by increasing its stability through it's spin rate.

Can you give an example of that? As I noted earlier, the Army tested the 55gr M193 in 1:14, 1:12, 1:9, and 1:7 and saw no difference in effect despite doubling the rate of twist (They also tested M855 in 1:9 and 1:7 with same results). If doubling the twist rate doesn’t delay a fairly light bullet like 55gr, I’m interested to see under what conditions that happens.

I believe that was at least part of the reason for adopting the faster twist in the M4.

The 1:7 twist was adopted in the M16A2 (1983) to stabilize the longer M856 tracer when NATO adopted SS109. The M4s (and most of the 14.5” AR-style carbine predecessors) just used the same twist as the A2 because they came later.

[marine6680]

We would need to get to the point that a man portable drone could be fielded that had the ability to deliver munitions...

At first it would be like small grenades and the like. Basically a free fall munition.

Guns and bullets are heavy and not suited for man portable drones.

There would still be an issue for enemies inside buildings or other defensible positions.


Now a drone capable of carrying actual firearms, that would need be on a transport, and you won't always have a support vehicle around.


It's an interesting idea and likely to happen, but not any time soon. Not until caseless is perfected.

Then you have the question of how close to the enemy will the drone get? That affects the ballistic needs.

[stagpanther]

It's an interesting idea and likely to happen, but not any time soon. Not until caseless is perfected.

Then you have the question of how close to the enemy will the drone get? That affects the ballistic needs.
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Wouldn't surprise me if China and Russia already have em.

[johnwilliamson062]

We have them in development. I am certain china russia and others do also. They aren't perfect. Some of the programs seem very misguided. Even small drones can curremtly have decent range at high speed. We dont think of them as such because they are legally limited to line of sight to all users in almost all locations in the US.
How often are us troops 15+ miles from transport? I can carry in one hand a drone with 20 pound payload, 30 mile range, and 100mph max speed and that is a model that hit civilian market 3 years ago.

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[marine6680]

But is it durable enough to handle field conditions in the hands of a soldier.

And carrying in one hand is not the same as small and portable enough to bring afield...

Sure a drone 2-3ft wide has decent payload, but they are too big for general use in field.

You need something no more than a foot wide for that use.

And a drone capable of 100km an hour likely can not do that well at max payload. And range can suffer.

Now I am not versed I. All of the high end drones, I dropped out of RC flight a while back, so I could be mistaken here.

[Mike Irwin]

I screwed that statement up. Pushing weight to the rear of the bullet INCREASES the tendency to tumble quickly, not the other way around.

Too much on my mind right now.

That's why bullets like the British Mk VII bullet had an aluminum nose filler (later versions had fiber fillers), a trait that was adopted by the Italians in the design of the 7.35 Carcano bullet.

Interestingly, .303 ammunition manufactured in the United States did not use the light weight filler, and were totally lead cored, resulting in a shorter bullet.

I've never heard anything one way or the other whether that affected lethality.

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[RC20]

All in all the 5mm adaptation was a copy cat like situation ala the US having to "match" the AK and its infamous 30 round magazine.

The two powers that did were conscript armies at the time.

We no longer are at all, they are more old style core lifers with the conscripts filling in the ranks. The 5mm may suit them.

It was a disastrous move for in Vietnam as the previous testing process was both aborted and then they screwed with the powder used as well as the magical needs no cleaning, probably the worst conceived introduction of a weapon system in US history. Full auto capability with conscripts was a recipe for and did lead to disaster (the so called insane mad minute)

There was not thought that lead to it and its weakness has manifested itself and should be corrected with a 6.5 mm Cartridge.

That would at least return a 1000 yard real capability and could unite the medium machine gun with the SAW weapon's as well as the rifles themselves.

Full auto capability should be restricted to weapons that can acualy do a true suppression role.

[johnwilliamson062]

https://www.outerplaces.com/science/...-duke-robotics
That is an unclassified item from over a year ago.
It is a crappy ad-hoc system. Look at all the weight used for ergonomic accessories that the drone doesn't take advantage of.

https://en.wikipedia.org/wiki/Autono..._Sniper_System
Although active, I believe this project failed to keep up with technology was back in 2010 and just sort of sits out there eating tax dollars.


Once the targeting is ironed out, using something like Lockheed Martins One Shot Sniper System a 9mm Glock 26 with a 33 round mag(or a larger capacity drum, or a pistol sized belt fed, would have plenty of lethality at ranges inside 100 yards. The weapons system can be surprisingly light once the aiming system is integrated.

But is it durable enough to handle field conditions in the hands of a soldier

.
There are very few things that fly and are known for robustness. Just the nature of flight that aircraft tend to be fragile. The items will likely mostly be vehicle serviced, but regular troops really aren't miles away from vehicles all that often anymore. Maybe used in unison with one of those robotic pack mules. In many instances the pack mules could be the weapons system. JSOC has the budget to ferry these in on Predators or similar.

The logistics of getting it into place will be small potatoes once they systems are ironed out. We built Aircraft Carriers in order to bring air power to the seas 100 years ago. This is way cheaper and simpler and we have learned quite a bit in the last century.

In direct confrontation with another world power there are all sorts of problems, but there are lots of US troops engaged in combat far from Russian and other advisors.

I'm a huge fan of the 6.5 in all its flavors. The US likely would have been better off adopting the Brit 280 or something, but it didn't happen. At this point I would be very surprised if general issue changes significantly from current until a new technology is used.

[marine6680]

While the roll out of the M16 was a crap show...

It was, from my understanding, said that the 55gr 5.56 ammo issued was regarded highly as an effective stopper. Being very effective terminally...

It did have issues with easier deflection in dense foliage though.


Issues with a weapon system do not discredit the ammo in and of itself.


And having a round capable of 1000yds is pointless as a general issue caliber. It is simply a flat out waste of resources and capability. (increased range comes at a cost of recoil and other negatives from a shooter perspective, and weight and amount of materials needed per cartridge)

I went through marksmanship training... While I personally never scored below expert qualification level, and often only a few points off of perfect scores... (toot toot)

You would not believe the percentage of recruits that were baffled by the whole concept of shooting a firearm.

Simple concepts like basic sight picture eluded them for days on end. I seen the epiphany myself in one recruits eyes, as the whole idea of sight picture finally clicked... This was on his last day of his second week of marksmanship training... He went from not hitting anything, to a barely passable score.

At least half of the recruits passed with bare minimums. Some from just having a lucky day... Others from generous shot calling from the guys pulling their target on their absolute last day of qualification, before getting recycled back to an earlier point in training, with a different platoon, if they failed again.


Tell me how those guys would benefit from a larger, heavier recoiling round, capable of being terminally and ballistically effective at 1000yds. (wind calls are already a pain at 500yds... but 1000?)

[marine6680]

And I work on aircraft... Lightweight is the game.

Shedding 50lb on a 10000lb plane is a big deal to pilots.


Fragile, not necessarily... But as you get smaller, Down to drone size, then fragile comes more into play.


Really it comes down to how you envision them being deployed, and how troops would be deployed and used.

[rickyrick]

I seen the same thing too with soldiers. Most barely qualify, many required more than one trip to the range to qualify.
I wouldn’t call meeting the minimum to qualify marksmanship on any level.

[stagpanther]

This talk is starting to depress me.

[rickyrick]

With the vast amount of new gun owners, I’m not sure if that equates to more kids having shot a gun prior to the military. Many expert marksmen learned how to shoot before they had enlisted.
My family has been in every major conflict of the USA. My family has two medals of honor, several silver stars and Purple Hearts. My own service did not yield any awards for valor. But as it went in my family, I was taught how to shoot as soon as I could support a rifle on my own. I knew how to shoot, even if it was this strange worn out but somehow futuristic looking rifle that rattled around and went “Sproingg” every time you pulled the trigger.

You receive lots of good training in the military, some training was frequent, most was effective in some way. Marksmanship training was mediocre at best and very sparse. Dry fire practice is a good thing to do, and we did lots of that in a short time period. I wasn’t an infantryman, so I don’t know what they do as far as marksmanship training goes.

My long wind rambling reply can be boiled down to this:
If training doesn’t get better, it doesn’t matter what bullet goes into the dirt.

[marine6680]

If my trips to the range are any indication... I doubt more gun owners will result in better shooting skill come recruit training.

Shooting pistols at 5yds with groups on the target that look like buckshot from 25yds.

That is the norm.


I'm out of practice lately, due to the increased difficulty in getting to a range regularly since I moved to Colorado... And I think I am shooting like crap, with 4-5in groups at 7yds rapid fire, double taps, etc... When I could do it in half the size before the move... (Not like I was great then either)

And I look like a freaking expert marksman compared to 90% of the people at the range.

[stagpanther]

Well, my technique and eyesight is pretty piss poor being a senior--except that I go out and shoot on average 3 or more times a week, so after years of that even poor technique gives way to some improvement. Hard to imagine young bucks with keen senses can't do a boatload better. I'm inclined to think it's not their fault. ; )

[rickyrick]

I’m a firm believer that everyone is good at something. A lot of people won’t be good at shooting, no matter what.

There’s not a type of person that joins the army, every type of person that exists in the civilian world, pretty much makes up the population of new recruits. Some just don’t have the aptitude, interest or even will to shoot a gun. To most range day is just another day of torture to get through, another box to check. Some people involuntarily close thier eyes every shot. Many will proclaim bent barrel and other equipment failures.

And yeah stag, when I had those 17 year old eyes, that country boy shooting ability, I could take that government M16 and get every hit, every time. When we’d do the substitute paper targets, I’d put each group in one hole. I learned that when we’d shoot the substitute paper targets, that I’d have to intentionally spread the groups to make sure the hits were counted. Sometimes they would only count one hole as one hit. By the time I joined the Army, I had many years of almost daily shooting experience. When I wasn’t out shooting firearms, I was also shooting pellet guns.
Now I can’t do those things.

I think the 5mm projectile for conventional force on force warfare is fine. I think for our modern conflicts like what this generation is fighting, I think the need just a bit bigger punch; like a millimeter or so.

[RC20]

It did have issues with easier deflection in dense foliage though.

Issues with a weapon system do not discredit the ammo in and of itself.

Per the people that study these things, deflection is not an aspect of the bullet.

The ammo had a powder substituted for what the gun was tested with. That powder was vastly more fouling. A cartridge and a gun are a system, change on everything you can and often do impact other aspect.

Add on the magic of it not needing cleaning (never true) but the cleaner powder and the lame powers in charge agreed.

And like the watermelon thing, people are not watermelon and they don't explored when hit with bullets..

If the 5.56 worked as more lethal it was because it tumbled as soon as it hit flesh. It is now too stable and poke holes.

I laughed when I saw the latest claims on the newest rounds. Penetrates and is lethal. Velocity and bullet design get moved by penetration not lethal. Its purely accidental if it acualy has good killing characteristics.

[Mike Irwin]

"That powder was vastly more fouling."

The primary reason the substituted ball powder was more fouling was that it contained excessive amounts of calcium carbonate designed to neutralize acids left over from the manufacturing process.

The calcium would build up in the gas port and gas tube and would quick reduce gas flow to the point where the gun had serious functional issues.

Studies showed that the calcium carbonate could be reduced to very minimal amounts that wouldn't result in gas port/tube fouling.

The reason ball powder was substituted at the last minute was that it could give a boost of nearly 100 fps (IIRC) over the velocities achieved by the original spec IMR powder.