5.56 NATO question

[Roboss]

This might seem like totally stupid question but why did the US Military decide to choose a 5.7mm(5.56) diameter bullet? I know that they went with a smaller and lighter bullet for more ammunition, but why for instance did they decide for a 5.7mm diameter? Why not 5.5mm or a straight up 6mm. What made 5.7mm just the right size?

Also what would be a good weight for a 6mm bullet? If the 5.56 now uses a 62 grain bullet, what what would be the appropriate weight for a 6mm?

 

[Texas10mm]

https://en.wikipedia.org/wiki/5.56×45mm_NATO

https://gundigest.com/gear-ammo/reloading/greatest-cartridges-the-rise-of-the-5-56x45-nato

http://looserounds.com/556timeline/

The last link should keep you occupied for a day or two.

 

[Roboss]

Thanks, I'll take a look at it.

 

[JohnKSa]

The bore/bullet diameter was a common one. So in that general size range it makes sense they would pick that specific bullet diameter. Plus, the design was based on an existing round that used that bullet diameter.

 

[jmr40]

Short version. They tried to make the already existing 222 round work. The 223 is a stretched 222 designed to get a little more powder capacity.

In reality there are very, very few new cartridges that are developed from a completely new cartridge case. Virtually all of them are based on a cartridge already in use that is modified. Most of the most popular cartridges used today are all based on the 7X57 that was developed in the 1890's. It's been shortened, lengthened, and made in calibers from 24-36 caliber, but the roots for all of them go back to 7X57. That includes 30-06 and all the cartridges based on 30-06 as well as 308 and all of the cartridges based on 308. The 7X57 is the grand daddy to all of them.

Now the 223 is the basis for multiple other rounds. based on the 223 case.

 

[army_eod]

Exactly. Started with a .222 varmint round.

 

[theotherwaldo]

Another reason for the 5.56 NATO is that the .222 round already had world-wide distribution, even in the countries that forbid civilian possession of military-caliber firearms... .

 

[Grumulkin]

This might seem like totally stupid question but why did the US Military decide to choose a 5.7mm(5.56) diameter bullet? I know that they went with a smaller and lighter bullet for more ammunition, but why for instance did they decide for a 5.7mm diameter? Why not 5.5mm or a straight up 6mm. What made 5.7mm just the right size?

Also what would be a good weight for a 6mm bullet? If the 5.56 now uses a 62 grain bullet, what what would be the appropriate weight for a 6mm?

What someone told me back when the military first started using it, it was because the velocity was so high that if the bullet hit you in the hand it would take your whole arm off.

 

[230RN]

I thought that hit in hand, take off your arm legend belonged to the .50 BMG cartridge. As far as I know, the only common round for which this is literally true is the 16" Naval Rifle round. And even that mighty projectile hitting your hand dead center would only take 8 inches off your arm.

Note:

Terry, 230RN

 

[Walkalong]

.22 caliber , .224, had been around a long time.

Remington's .223 and .222 Mag data used to be identical, the Mag has 5% more capacity but runs at a lower pressure, unless you hand load of course.

The 5.56/.223 is basically a .222 Mag with the shoulder moved back, more body taper, overall a hair shorter, running higher pressure.

 

[mokin]

I thought that hit in hand, take off your arm legend belonged to the .50 BMG cartridge. As far as I know, the only common round for which this is literally true is the 16" Naval Rifle round. And even that mighty projectile hitting your hand would only take off 8 inches of your arm.

Note:

Terry, 230RN

Gel tests or it ain't true.

 

[herrwalther]

The 222 Remington round has been around since 1950. Choosing a 62gr projectile for the 5.56 was no accident. Post WWII, big Army was looking into making lighter weapons and ammo. Adopting the M14 and 7.62x51 was a baby step down from the M1 and 30-06 compared to the M16 and 5.56.

 

[.308 Norma]

If the 5.56 now uses a 62 grain bullet, what what would be the appropriate weight for a 6mm?

Just like there's a lot of cartridges out there that use 5.56/.223 bullets, there's a lot of cartridges that use 6mm bullets. The "appropriate" weight for a 6mm bullet depends on what cartridge you're figuring on using it in, but mostly it depends on what you're figuring on doing with it. My dad and my wife have killed a lot of mule deer with .243 Winchester cartridges firing Speer and Remington 100 grain, 6mm/.243 bullets.

 

[danez71]

I thought that hit in hand, take off your arm legend belonged to the .50 BMG cartridge.

I thought it was....

.50 BMG would take your head off if it just wizz by near it.

.44 Mag will take your arm off if you get hit in the hand.

5.56 because it drains more resources to care for a wounded soldiers.

 

[Swampman]

This might seem like totally stupid question but why did the US Military decide to choose a 5.7mm(5.56) diameter bullet?

Probably just adding insult to injury after shoving .30 caliber down the throats of our protesting NATO allies a dozen years before, .224" being another traditional American caliber.

...The 7X57 is the grand daddy to all of them...

The 8x57 came out almost half a decade before the 7x57. It has the same case head and length. You can make 7x57 easily by necking down 8x57.

The 7.65x54 was a Mauser design that came out in 1889, 3 years before the 7x57, it has the exact same case head.

Why do you consider the 7x57 to be the "grandaddy" to all .473" head cartridges when it wasn't anywhere near being the first of them?

 

[Archie]

Why do you consider the 7x57 to be the "grandaddy" to all .473" head cartridges when it wasn't anywhere near being the first of them?

Likely from a You Tube post titled "The Big Daddy of All - the 7x57mm Mauser". The narrator of that video essentially tells that tale and forgets - or is unaware - of the 8mm, actually 7.92x57mm - Commission Rifle and cartridge. Other than that, it's pretty correct.

"The operation was a success, but the patient died anyway".

 

[mjsdwash]

Short version. They tried to make the already existing 222 round work. The 223 is a stretched 222 designed to get a little more powder capacity.

In reality there are very, very few new cartridges that are developed from a completely new cartridge case. Virtually all of them are based on a cartridge already in use that is modified. Most of the most popular cartridges used today are all based on the 7X57 that was developed in the 1890's. It's been shortened, lengthened, and made in calibers from 24-36 caliber, but the roots for all of them go back to 7X57. That includes 30-06 and all the cartridges based on 30-06 as well as 308 and all of the cartridges based on 308. The 7X57 is the grand daddy to all of them.

Now the 223 is the basis for multiple other rounds. based on the 223 case.

The most interesting one I have found that goes back to that case head is the 45 ACP. Maybe not exactly a "parent case", but can be made from it.

 

[entropy]

This might seem like totally stupid question but why did the US Military decide to choose a 5.7mm(5.56) diameter bullet? I know that they went with a smaller and lighter bullet for more ammunition, but why for instance did they decide for a 5.7mm diameter? Why not 5.5mm or a straight up 6mm. What made 5.7mm just the right size?

Also what would be a good weight for a 6mm bullet? If the 5.56 now uses a 62 grain bullet, what what would be the appropriate weight for a 6mm?

Because they started with the .222 Remington for a base round.

 

[alsaqr]

There was a requirement that the bullet penetrate a helmet at some specific distance. That requirement could not be met using the .222 case. The case was lengthened to hold a few more grains of powder.

 

[Jim Watson]

The requirement was to penetrate a US helmet at 300 yards.
Back when Guns & Ammo was a moderately technical publication, one of their regulars wrote that he was in on the development and demonstrated that it was possible for a 22 by blending powders to do it with a .222. The load he came up with was still classified at the time. No doubt pressure was high, so more case volume was needed. Remington developed the .223 from the .222 Magnum and Winchester had the similar .224 Win. They were one-way interchangeable, you could shoot the Remington ammo in the Winchester rifle or vice versa and I don't remember which way.

The original .222 was an oddball, a very successful one but not based on any existing cartridge. Remington's first look at a varmint round in 1950 was based on the .30 Remington, kind of a .219 Zipper Rimless, but they concluded that the .30 brass blank would not give enough head thickness for the pressures expected. I don't know why they didn't just beef up the .30 but instead came out with a whole new design.