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mattmcg
09-30-2008, 12:57 PM
We see this question posted at least once a week and after answering it a number of times, I decided to publish my thoughts into a cohesive article discussing the differences between 223 Remington and 5.56mm NATO ammunition. I cover safety issues as well as a few reloading points. Hopefully this will answer some of the questions that our newer members are asking about the differences between the two. Mods, feel free to make this a sticky if you like.

Here is the link:
What is the Difference Between .223 and 5.56 Rifle Cartridges and Chamberings? (http://home.comcast.net/~mattmcginnis/reloading/223_versus_556.htm)

JTecalo
09-30-2008, 1:02 PM
We see this question posted at least once a week and after answering it a number of times, I decided to publish my thoughts into a cohesive article discussing the differences between 223 Remington and 5.56mm NATO ammunition. I cover safety issues as well as a few reloading points. Hopefully this will answer some of the questions that our newer members are asking about the differences between the two. Mods, feel free to make this a sticky if you like.

Thanks for the info and the link!

nick
09-30-2008, 1:07 PM
Problem is, seller often confuse the two.

For example, I've recently saw Army surplus that I presume was 5.56x45 advertized as .223.

For that matter, I'm still trying to figure out (haven't received it yet) whether the Saiga I ordered here is a 5.56x45 or .223 Rem:

http://www.rrarms.com/catalog.php?prod=GIZ114

mattmcg
09-30-2008, 3:15 PM
Problem is, seller often confuse the two.

For example, I've recently saw Army surplus that I presume was 5.56x45 advertized as .223.

For that matter, I'm still trying to figure out (haven't received it yet) whether the Saiga I ordered here is a 5.56x45 or .223 Rem:

http://www.rrarms.com/catalog.php?prod=GIZ114

You can always make a cast of your chamber and measure it to see what specs it abides by. You can use a casting alloy to get the exact blueprint which is very helpful for reloading specs.

I get this stuff from MidwayUSA CerroSafe Casting Alloy (http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=462291)

nick
09-30-2008, 3:49 PM
You can always make a cast of your chamber and measure it to see what specs it abides by. You can use a casting alloy to get the exact blueprint which is very helpful for reloading specs.

I get this stuff from MidwayUSA CerroSafe Casting Alloy (http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=462291)

Complicated. I live in an apartment, and I don't even have the space for the tools, much less casting something :)

-hanko
09-30-2008, 7:38 PM
Problem is, seller often confuse the two.

For example, I've recently saw Army surplus that I presume was 5.56x45 advertized as .223.
Which is why it's recommended to ask the seller about the headstamp;)

-hanko

nick
09-30-2008, 7:43 PM
Which is why it's recommended to ask the seller about the headstamp;)

-hanko

And hope the Russians got it right :)

rtlltj
09-30-2008, 8:13 PM
Thanks for the article. It's helpful to link this or show someone instead of trying to explain to them that it's not just the metric conversion thats different. I noticed its usually the people who shoot 223 bolt actions only who don't really know the real differences.

m24armorer
10-01-2008, 12:40 AM
The difference between the 223 Remington and 5.56mm NATO chambers are in the throat area (also called the "Leade" area). This is the portion of the barrel directly in front of the chamber where the rifling has been removed to allow space for the seated bullet. The throat in a 223 Remington chamber is typically .085" while the throat in the 5.56mm chamber is typically .162". The added space in the 5.56mm chamber compensates for the added pressure inherent in the 5.56mm NATO round.

So is it the chamber or the throat? Added space in the chamber?

Not trying to be contrite but it just did not make sense to me.

till44
10-01-2008, 9:04 AM
Great article.

scubamark13
10-01-2008, 9:26 AM
Very informative. Thank you.

mattmcg
10-01-2008, 10:08 AM
The difference between the 223 Remington and 5.56mm NATO chambers are in the throat area (also called the "Leade" area). This is the portion of the barrel directly in front of the chamber where the rifling has been removed to allow space for the seated bullet. The throat in a 223 Remington chamber is typically .085" while the throat in the 5.56mm chamber is typically .162". The added space in the 5.56mm chamber compensates for the added pressure inherent in the 5.56mm NATO round.

So is it the chamber or the throat? Added space in the chamber?

Not trying to be contrite but it just did not make sense to me.

Coming from a man that surely knows the difference..... ;) I can see with how I've written it, it might be a tad confusing.... Chamber versus chambering...

I've made a few updates to the article to clarify the term usage and have added further depth into what the throat consists of including "freebore" and "leade" definitions.

Ironchef
10-01-2008, 11:06 AM
So, if I get a 5.56 chambered upper, which I will eventually (after getting a .22lr upper), and when I use .223 ammo..I"m wondering how much pressure is lost, how much accuracy is lost, etc..when shooting that .223 cartridge..since there is a jump from the chamber into the flats as described. I like the idea of the wylde chamber shortening that jump the bullet makes. I'm just concerned about that gap. Do upper manufacturers make .223 chambered uppers anymore? Seems like you'd want that (assuming you'll only shoot the .223 rounds) instead of having the inconsistent round placement from a 5.56 chamber.

I realize my questions probably ONLY effect long range precision shooting..but still. If you're investing the money in a beautiful black rifle...why not have exact fits?

Also, is 5.56 nato ammo roughly the same cost as the average .223 cartridge cost? Which is more abundant? More reliable?

DVLDOC
10-01-2008, 11:39 AM
GREAT ARTICLE! The only thing that confuses is that when buying ammo is that some manufacter like SILVER BEAR/WOLF will print ".233 (5.56)" or "5.56 (.223) on the box. So I'm like which on is it?

mattmcg
10-01-2008, 1:14 PM
Ok, to answer a couple of your questions

I'm wondering how much pressure is lost..
So it's not an issue of pressure lost, it is just that the pressure curve and maximum are lower. This is not necessarily a bad thing. Higher pressures normally lead to higher velocities but also heavier wear on components as well as possible component failures (when exceeding a component maximum).

how much accuracy is lost...
I'm sure there are some long-range practical and benchrest shooters amongst the group here that can weigh in, but larger jumps causing a reduction in consistency (leading to a reduction in accuracy) is a highly debated topic. The theory is that the larger jump allows minor variances in how the bullet engages with the lands and begins to spin. These variances lead to less consistency leading to less accuracy (the perfect scenario is a perfectly consistent round to round cartridge fired at exactly the same spot. This would be "perfect accuracy" if there is such a thing).

That said, my personal belief is that a very small but reasonable level of bullet jump of .002" is within the realm of approaching perfect consistency while retaining a slight margin for safety purposes. There are some very experienced benchrest shooters that will seat their bullets to just kiss the lands and believe this allows zero variance from round to round. We should all aspire to be able to produce such ammo for our rifles but it is extremely impractical.

I like the idea of the wylde chamber shortening that jump the bullet makes. I'm just concerned about that gap.
I also am a big fan of the 223 Wylde chamber. I have two rifles with Wylde chambers and when shooting 223 seated .002" from the lands, it is an absolute tackdriver (.5" @ 100 yards).

Also, all production rifle ammo will have a gap in between the bullet and the lands. This is the norm and a safety thing. Also, in an AR platform, you must seat a bullet so the maximum is less than 2.260" to even fit into standard AR mags. For my 223 Wylde chambered AR, seating it the lands is much longer than that (of which I use a different mag insert to simply fit 1 round to feed it into the chamber).

Do upper manufacturers make .223 chambered uppers anymore? Seems like you'd want that (assuming you'll only shoot the .223 rounds) instead of having the inconsistent round placement from a 5.56 chamber.
Frankly, I don't know if anybody still makes a 223 chambering in an AR upper. Most have gravitated fully to the 5.56 NATO specifications with some falling back to the 223 Wylde to improve the accuracy of 223.

I realize my questions probably ONLY effect long range precision shooting..but still. If you're investing the money in a beautiful black rifle...why not have exact fits?
Yes, funny you would say that. It would seem that it would have been simpler to simply abide by a simple standard. It would have definitely made this whole mess a lot easier. America has a funny way of "standardizing" when you think of the US Imperial system of measurements compared to the metric system. Heck, we even have different telecom system standards from the rest of world (GSM vs CDMA). Nothing ever comes easy..... :rolleyes:

Also, is 5.56 nato ammo roughly the same cost as the average .223 cartridge cost? Which is more abundant? More reliable?

I'll leave this to the ammo hounds here as I tend to futz around with smithing some of these items rather than shooting (bad, I know). My experience is that 5.56 NATO in bulk is a bit cheaper but still shoot 223 Rem for the most part when building handloads or competing.

mattmcg
10-01-2008, 1:17 PM
GREAT ARTICLE! The only thing that confuses is that when buying ammo is that some manufacter like SILVER BEAR/WOLF will print ".233 (5.56)" or "5.56 (.223) on the box. So I'm like which on is it?

Ok, this is an easy confusion to solve. .223" = 5.56mm. This is a simple conversion from inches to millimeters. Simple enough. So the box is accurate and is probably meant to denote both systems of measurements for the diameter of the bullet.

Now, if the box says "5.56 NATO" or "5.56x45" and has a small circle with a + sign in the middle of it on either the box or the case head, then you've got 5.56 NATO rounds (with all safety warnings that apply for firing in 223 Remington firearms).

Here are some examples of essentially the same ammo but 223 Rem with one vs 5.56 NATO for the other:
Hornady 223 ammo (http://ammunitiontogo.com/catalog1/product_info.php?pName=20rds-223-hornady-tap-leo-75gr-hp-ammo&cName=223-556-hollow-point-ammo)
Hornady 5.56 ammo (http://ammunitiontogo.com/catalog1/product_info.php?pName=20rds-556-hornady-tap-75gr-bthp-t2-ammo&cName=223-556-hollow-point-ammo)

Lon Moer
10-01-2008, 5:21 PM
I can't believe nobody has posted this link(?) Ammo Oracle (ammo.ar15.com)

m24armorer
10-02-2008, 9:04 PM
I'll pull the prints when I have a chance. A Obermeyer throat is another to consider.

ar15barrels
10-03-2008, 9:50 PM
I'll pull the prints when I have a chance.

Or you could just link to this. ;)

www.ar15barrels.com/data/223-556.pdf

mattmcg
10-03-2008, 11:07 PM
Or you could just link to this. ;)

www.ar15barrels.com/data/223-556.pdf

Nice schematic Randall!

ar15barrels
10-04-2008, 9:27 AM
Nice schematic Randall!

No 223 vs. 5.56 thread is complete without it...