5.56mm NATO versus 223 Remington Chamber Differences

[SgtRock]

Great post... really detailed...

[patrick sweeney]

I'd consider carefully any mention of a Wylde chamber popping primers.

Factory ammo? Or reloads? Remember, the guys in the before-now times who were using a Wylde chamber were most likely High Power competitors. Some of them loaded so hot that they considered brass a one-use commodity.

So, just because ti has a Wylde chamber, and the brass was thrashed, doesn't mean it was because it had a Wylde chamber.

[rcoodyar15]

One thing I will add right up front is I personally would never fire a 5.56 round in a .223 chambered rifle.

Now don't get me wrong about what I am about to say.

The actual chamber pressure of a 5.56 round fired in a 5.56 chambered rifle is very close if not Identical to the chamber pressure of a .223 round fired in a .223 chamber.

Now granted 5.56 rounds are loaded hotter but because of the dimensions and construction of the 5.56 chamber the larger powder charge do not result in higher chamber pressures. But if you put this load in a .223 chamber you are basicly looking for trouble.

The confusion comes because of the different methods used to measure the chamber pressures. If you look at the original specs for the 5.56 it plainly states SAMI 55000 psi. same as .223.

here is a link explaining this

http://ballistictools.com/articles/5...-and-facts.php

[MistWolf]

...The actual chamber pressure of a 5.56 round fired in a 5.56 chambered rifle is very close if not Identical to the chamber pressure of a .223 round fired in a .223 chamber...

Now granted 5.56 rounds are loaded hotter but because of the dimensions and construction of the 5.56 chamber the larger powder charge do not result in higher chamber pressures...

These two statements contradict each other. It's generally accepted that a "hotter" load is one that's loaded to greater pressure. Although the 5.56 takes more powder to make the same pressure in a 5.56 chamber than a 223 does in a 223 SAAMI chamber, that doesn't make the 5.56 "hotter". (Of course, firing a 5.56 in a minimum spec SAAMI chamber does result in raising the pressure)

What also muddies the waters is that not all NATO ammo is loaded to NATO pressure. Some is loaded to lower pressure. Some NATO ammo suffers wide variation in pressure from lot to lot

[rcoodyar15]

These two statements contradict each other. It's generally accepted that a "hotter" load is one that's loaded to greater pressure. Although the 5.56 takes more powder to make the same pressure in a 5.56 chamber than a 223 does in a 223 SAAMI chamber, that doesn't make the 5.56 "hotter". (Of course, firing a 5.56 in a minimum spec SAAMI chamber does result in raising the pressure)

What also muddies the waters is that not all NATO ammo is loaded to NATO pressure. Some is loaded to lower pressure. Some NATO ammo suffers wide variation in pressure from lot to lot

Hotter An unfortunate choice of words. What I was really refering to was velocity. Granted the pressure is the same but the larger powder charge and chamber configuration in the 5.56 does result in higher velocities. 55gr 5.56 about 3200 fps average 55gr .223 3000 fps. I am sure there are exceptions. fact is there is a wide range for both.

then there is what you can accomplish with handloads.

[MistWolf]

Hotter An unfortunate choice of words. What I was really refering to was velocity. Granted the pressure is the same but the larger powder charge and chamber configuration in the 5.56 does result in higher velocities. 55gr 5.56 about 3200 fps average 55gr .223 3000 fps. I am sure there are exceptions. fact is there is a wide range for both.

then there is what you can accomplish with handloads.

Gotcha.

As has been explained over and over again, the 5.56 uses a long throat to get that increase in velocity by effectively increasing case capacity. It's the same trick Roy Weatherby used to eke out the last bit of velocity from his line of magnums. It's also one detail that kept other companies from offering more than a handful of rifles in Weatherby calibers

[rcoodyar15]

yeap

more volume for the gas from the burning powder

and

let that bullet get a running start before it hits the rifling

[Tango4N]

So are there any bolt guns in 5.56?

[LRRPF52]

The barrel maker can stamp anything on the barrel. The questions I have come to over the past few years are:

Who made the reamer, who inspected it before they threw it in the breech (at an angle of course-can't have concentric chambers to the bore now can we), and how many extra cycles was it run after it needed to be sharpened or scrapped?

What reamer prints were used when the tool maker had his THC-enriched blood content employee grind it, and did the barrel maker ask for certs?

The companies with a reputation have learned the hard way to go over their reamers with a fine toothed comb, whereas I suspect most of the market operates on trust, without verification. "Screw it, let the customer suck up our failures. They're not going to shoot these things anyway."

This is one of the laundry lists of reasons why I haven't bought a rifle off the shelf since 2007. If someone were to ask me to pick a solid 5.56 blaster barrel right now, you have 3 seconds to make your choice, it would be a quick answer for me: BCM or DD, and that's based on years and years of witnessing them in conditions you just don't see in the US, unless you go into Alaska in the dead of winter.

Run a gun in hot weather, where it loves to be-no problem. Run it at the edge where you start to wonder if primers are even going to light because of the sub-zero cold, like -30 C, and weird things start to happen. This is where you find out why the military has Arctic testing as one of the major hurdles for vetting a weapon system.

Chamber dimensions are critical in that regard. So is quality brass-cased ammo.

[MaxLoad]

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