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Yes I have read the explanation of some slight differences in the 5.56 and the .223 but has anyone ever heard of anyone having a problem with this? Has anyone heard of a barrel exploding, anyone being hurt?, any kind of damage to the firearm. Also want to know if reloading a 5.56 casing using .223 dies is it then going to be a .223 after resizing in the .223 die?
 

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No. The external cartridge dimensions are identical for all practical purposes and not counting the odd metric conversion rounding errors in the last decimal place.

The only significant physical difference I am aware of is in the standard chamber dimensions. The military chambers are more generous for more reliable full-auto operation.

The only other physical difference is an illusion in difference in pressure numbers created by the two different measuring systems: the one used by our NATO allies and the one used by the U.S.

The NATO rounds are specified by the NATO EPVAT documentation as having 430 MPa (62,366 psi) maximum average (peak) pressure (MAP) in a sample lot of newly loaded ammunition, which the CIP also uses as the European commercial specification. Both are measured by a Piezo transducer using drilled cases venting against a piston with a gas check like a lot of copper crusher systems do.

The military in the U.S., specifies the same ammunition under SCATP 5.56 documentation as having a MAP of 380 MPa (55,114 psi). Same as SAAMI, they use a conformal pressure transducer that has a piston that matches the contour of the chamber so the brass is not drilled and the pressure is measured on the brass surface and not inside the case as the other system does it. SAAMI rounds down the last 114 psi to uses 55,000 psi, even, as their MAP, but otherwise it's identical to the U. S. military spec.

The testing methodologies are not the same, and this appears to account for the numerical pressure number discrepancy. These different results are obtained with the exact same reference ammunition fired in both setups, so the actual ammunition pressures are no different.
 

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The Shadow (Super Mod)
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As nick said, it's the essential same. The brass is also the same, the throats can be different. But so can two rifles from the same production line...
There is something like eleventy-billion surplussed rounds sold to the private sector every year, they aren't only sold to a verified NATO chambered gun, and there aren't eleventy-billion blown-up folks every year either.

Around a year ago I called the brass producers of the US, which was not an easy feat. Then I called them all back later to try and get a different story, and never did. The brass differs in headstamp only.

A crappy quarter pounder with cheese, is a crappy quarter pounder with cheese; even if the box says Royale with cheese.

Here is a gent who did just as you asked, with a pressure trace.
How many reloaders who have "stout" loads use a pressure testing device? What are their loads really doing...
http://www.luckygunner.com/labs/5-56-vs-223/
 

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.223 chambers are made with a shorter leade and steeper throat angle to enhance accuracy. 5.56mm cartridges are loaded to slightly higher pressure, and the 5.56mm chamber has a longer leade ( freebore before the rifling starts), and a shallower throat ( less angle). This was for longer, heavier bullets like the tracer round. If you are out shooting in the sand box on a very warm day, you don't want a blown primer falling down and tying up your trigger. For the military , reliabilty trumps extreme accuracy. This brought about the Wilde chamber, which is a blend of both. But as Darkker says even rifles from the same production line can differ. Patrick Sweeney has tested a few dozen rifles marked with 5.56mm on the barrel and found several that did not have a true 5.56mm chamber. Any .223 rifle that one wishes to "open up" to a 5,56mm chamber can be done with a MichiGuns reamer with just a few twists of the tool.
Rifles are tested with proof loads that are some 30% over. People shoot 5.56mm in their .223 chamber all the time without disastrous results. Maybe, on a hot day, you could get a blown primer, it would be good to have on some eye protection.
 

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If you look closely at the two graphs in the video Darkker linked to, you find pressure varied almost 10% and velocity only varied 1.2%. For anyone entertaining the idea they can tell pressure from velocity, let that be a warning.

All those pressures fall within the pressure standards which, as I explained previously, are actually the same, currently. There have been intermediate copper crusher test methods that have stretched the differences in the past, but board member Humpy, a former Aberdeen Proving Grounds Test Director, said his contacts there say it's all changed over to the conformal Piezo transducer system now.

The SAAMI standard 223 Remington test barrel has a freebore that is 0.025". Actual commercial .223 Remington reamers cut freebores ranging from 0.025" to 0.068". The 5.56 NATO freebore is usually given as 0.050", but reamers range from 0.050"-0.0566". See dimension N in the reamer comparison chart, here.

Does an extra 0.025" of freebore make a significant pressure difference with standard ball ammunition? No. The graphs in Darkker's link show that other factors are more important, as one of the 5.56 chambers in those measurements had higher pressure than the commercial .223 chamber did, and one was lower. Everyone remembers Roy Weatherby designed his magnums with long freebores to lower peak pressure, but to get peak pressure down, those Weatherby freebores are a full caliber long; much longer than either the 5.56 NATO or .223 Remington freebores.

Both 7.62 NATO and 5.56 NATO have the longer chamber freebores mentioned in order to handle specialty ammo, as already described. If you are unsure whether you have such a round, get one of the cartridge overall length gauges and comparator tools that measures bullet position off the ogive, like the Hornady or Sinclair units. (Note there are lots of homebrew methods you can search for on this forum.) Measure a dummy or gauge that just touches your throat, then do the same with the questionable ammo to find out if it's too long for your chamber. I prefer the Sinclair stainless bullet comparator inserts for this (they also fit the Hornady/Stoney point caliper adapters) over the Hornady, as they are based on matching actual throat profiles, so they touch the bullets further down where they will actually contact the throat.
 

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Bottom line short of a bore obstruction the risk of something happening is no greater than pulling the trigger on one round to another.

whether you are shooting a .22 or a .50 BMG eye protection along with a strong use of your brain is always the best protection.

good luck
Shoot straight and shoot often
GF
 

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Even though this is an old post I re-read stuff to re-learn or remember stuff I already read before. I thought I'd make a comment. Somewhere or other I read that one can have problems when using re-loading data for .223 cases in 5.56 military cases due to the fact that the military cases are thicker (and heavier) and consequently have less internal volume. Same amount of powder in less internal volume= higher pressures. Now, I'm NOT a re-loader and have never weighed civilian and/or military cases, but, If this is true, that military cases have less internal volume, it would be something for re-loaders to consider and take into account.
I leave it for those with experience in these matters (as I have none) to comment.

Luisyamaha
 

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The Shadow (Super Mod)
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Somewhere or other I read that one can have problems when using re-loading data for .223 cases in 5.56 military cases due to the fact that the military cases are thicker (and heavier) and consequently have less internal volume.
That is a common mistake and taken advantage of in marketing very frequently.
Many times Brand A is heavier than brand B, or even from lot to lot; but as I have said in several of my loading posts, Weight and Volume are not the same thing.

If you hold a 1" cube of steel and compare it to a 1" cube of lead, one weighs more than the other. So does that mean that the heavier actually has more volume? Of course not; you are talking different things.
Similarly, there is no singular unchanging "mixture" that can be, or in fact does get used, to make cartridge brass. So the weight can be different regardless of whether or not the volume also differs.

If you presume that any difference in weight therefore requires a change in volume, you could be correct in any specific example, but as a principle, are incorrect. Most recently look at my post from this past thanksgiving, where I pressure tested Creedmoor brass. The weight of the Lapua and the Norma brass was notably different. When loaded with the same powder charge and bullet, the resulting pressure curves were identical. As another factor that aggravates the presumption, is normal manufacturing variance. I can't recall the specific arsenal name at the moment(don't think it was Pic) did testing way back concerning dropped primers and the claims of the CaCO in WC846 in the 5.56. They tested some insane amount of ammo like several hundreds of thousands of rounds to get the answers. Part of what that testing showed was that even from the same line with the same machines there was a normal range of case capacities that were produced. Now add in a line with say a dozen different machines and different states of wear on them. There simply isn't any way to have identical capacities in every piece of brass, in mass produced things.

So it has become vogue to weigh cases, some mfgrs even market very sucessfully that fact; and it is assumed or implied that somehow that makes all variation in capacity magically dissapear; when in truth is has not, nor cannot.


I have posted this before in a thread which speaks to my point. As I've said before, I have had this for so long, I have no clue where it came from. I'd give credit where due, but no clue on it's origin.

 
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The Troll Whisperer (Moderator)
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Well............ With that, I'd have to say it makes little difference which type of case you use. I've always had a mix of commercial and military. Kept them separate, of course, but still fired all of them in Ruger actions, some factory barrels and others of aftermarket makers. Nary a problem.
 

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Elk Whisperer (Super Moderator)
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Darrker, you don't know the average H2O capacity of RP brass by chance. I can go weigh one if you don't. Are you weighing new unfired?

RJ
 

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if you have two cases that are fire formed in the same chamber, and one weighs more, it would have to have less capacity I'd think. Yes, there could be slight differences in the density of the brass, but I'd think for all practical purposes, that difference would be slight. And if the two cases are from the same manufacturer, I'd guess there is very very little difference in the bras formulation. Where else could the weight differenc be if it's not from more volume of brass within the volume the case takes up. Now, rather slight differences of internal volume actiually have a meaningful difference in pressure, I don't know.
 

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The Shadow (Super Mod)
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Darrker, you don't know the average H2O capacity of RP brass by chance. I can go weigh one if you don't. Are you weighing new unfired?

RJ
if you have two cases that are fire formed in the same chamber, and one weighs more, it would have to have less capacity I'd think. Yes, there could be slight differences in the density of the brass, but I'd think for all practical purposes, that difference would be slight. And if the two cases are from the same manufacturer, I'd guess there is very very little difference in the bras formulation. Where else could the weight differenc be if it's not from more volume of brass within the volume the case takes up. Now, rather slight differences of internal volume actiually have a meaningful difference in pressure, I don't know.
RJ -
I don't. I'm on the road for a daughters volleyball tournament, and haven't had a 223 in a decade. IIRC, the chart was an average from something like 20 pieces.

Swift-
Minor differences are less minor than you think, at times. I'm to lazy to dig it up, but search my name and find the Thanksgiving test. Creedmoor brass was different by over 10 grains; but pressures were identical. And from a very old thread I did about loading by volume, same was found in the 308, where I personally measured brass. It has to be somewhere online still, but the Arsenal testing on the 5.56 brass had some stunningly large variations. The place I knew it to be is now gone. Nick or Humpy have some inside knowledge of the Arsenals and may have that info handy.
 

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RJ -
I don't. I'm on the road for a daughters volleyball tournament, and haven't had a 223 in a decade. IIRC, the chart was an average from something like 20 pieces.

Swift-
Minor differences are less minor than you think, at times. I'm to lazy to dig it up, but search my name and find the Thanksgiving test. Creedmoor brass was different by over 10 grains; but pressures were identical. And from a very old thread I did about loading by volume, same was found in the 308, where I personally measured brass. It has to be somewhere online still, but the Arsenal testing on the 5.56 brass had some stunningly large variations. The place I knew it to be is now gone. Nick or Humpy have some inside knowledge of the Arsenals and may have that info handy.

I don't doubt there is 10 grains difference, or that pressures were the same. But my thinking is 10 grains just isn't enough to make a difference. On a 6.5 creedmore case, 10 grains of brass would be the equivalent of reducing the case body diameter .004. Just doesn't esteem like much. And since brass weighs 8.5 times as much as water, slight differences would be hard to measure, being that 10 grains of brass would equal slightly over 1 grain of water.
 

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The Shadow (Super Mod)
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Here's the bottom line, measure and you'll know; but the domestics told me the headstamp is the only difference.

Steve over on the 1911 board did a bunch of this as well, and had weight and capacity side by side.
https://forums.1911forum.com/showthread.php?t=424598#/topics/424598

That chart shows There is no correlation. Just when you think things match, they don't.
Or my volume Vs. weight thread, or this:
https://www.google.com/amp/s/www.gunsamerica.com/blog/reloading-science-do-you-really-need-to-sort-your-brass/amp/

Don't confuse marketing magic with reality.
 

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Elk Whisperer (Super Moderator)
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Darkker, I will do a test today and post the results so you can add them to your data.

RJ
 

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original Vietnam 5.56 with 55 grain fmj is the original standard for .223 Remington and 5.56x45 Nato.


The issue is that the "XM 193" 55 grain stuff SHOULD ONLY be laoded to the original 5.56=.223 Remington standard.


The MOST common comment/warning is based upon the NATO modifications to the chamber throat.

That was done so they could use tracers and heavy bullets for newer rifling twist rate.

That creates several problems if you read carefully.

1. All sources CLAIM that a standard .223 Remington chamber made to the original chamber throat/lade measurements CANT provide sufficient room to chamber a bullet over 55 grains.

1A I have seen thousands of thread postings from people owning .223 Rem marked ARs that run 5.56x45 nato ammo in 60+ bullet weights with no feed issues or sign of the over sized bullet profile jamming in the leade.

1b Thousands of people have told us how they borrowed a "true" 5.56x45 Nato reamer and hand turned it to make their chamber leade a true "5.56x45 NATO"

1c The gunwriters claim the AR industry uses the same 5.56x45 Nato modern throat reamer to make ALL NON TARGET GRADE .223 Remington Rifles

1dThe gun industry has yet to say what specific profile is actually used for bolt action rifles

2. Actual pressure levels of 5.56x45 Nato

2a NATO has a load standard based on bullet used. THERE IS NO PROOF that civilian made 5.56x45 follows those same pressure standards
Meaning it is POSSIBLE that some civilian company can load 55gr Xm193 to the same 62,800 PSI level of the newest 68 grain military ammo and be "safe" doing it.

2b I talked to FEDERAL on this all, and from their supplied rough ballistic data, their xm193 55 grain FMJ and their .223 Remington 55 grain ammunition is the same thing in a different head stamp

2c If using the proper cartridge was critical, then why have so many people purchased VIETNAM produced rifles designed for .223 Remington successfully used CASES of modern 5.56x45 with no ill effect to these old as crap guns?
 

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The Shadow (Super Mod)
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Yep, and look at anyone else's reamers, they are different. Then look at the SAAMI chamber spec....
Then for some real fun, jump to CIP, and note they are identical.

Cheers
 
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