In the past 60 or so years there have been millions of guns chambered in both .223 and 5.56 sold. Over that same 60 or so years there has been hundreds of millions of .223 and 5.56 ammo sold and shot out of them. If it was really an issue you would think that there would be thousands of examples of blown up guns to be seen. Also if it was really an issue both SAAMI, the gun manufacturers, and the ammo manufacturers would have gotten together long ago and made one standard to protect stupid people from hurting themselves.
.223 Rem vs. 5.56 NATO Chambers/Overpressure Issues?
- Thread starter JeepHammer
- Start date
JeepHammer
Moderator
Jim,
Mostly because I couldn't twist my head around the issue for reloading, and I've tried for quite a while.
I'm crystal clear on the machining/processes end of things,
This is one of those subjects with so many variables it's actually a little hard to grasp and cook down into one blanket statement.
Sorry if it ruffled your feathers, I'm just looking for some Go/NoGo lines you shouldn't cross.
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I'm with Clark, I got an 'AR-15 Upper, Generic' in a trade for some parts that had a chamber so tight nothing fit into it.
Bore scope showed a REALLY dull reamer, metal smearing, gouges, a bore that looked like it was cut with an old brick.
It's a really nice bar over the camp fire pit now.
Wasn't going to cut the chamber, then try and lap the bore out smooth for the $120 it takes for a new barrel...
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TMD,
There are a bunch of 'In Between' chambers/reamers on the market, you have to be specific you want a STRICTLY SAAMI chamber reamer these days to get a strictly SAMMI specification throat.
Some barrel manufacturers have their own chambers that are 'In Between' you normally can't find the reamer on the open market. Proprietary, more or less.
Some have gone to the trouble of getting SAAMI recognition, like the Bill Wylde chamber (.223 Wylde), Some haven't.
I just a Geek from the country that casts/gauges chambers, and I rarely run in to a 'Strict' .223 Rem chamber or 'Strict' 5.56 chamber anymore unless it's on an older civilian rifle, or on a military barrel, almost everything is 'In Between' to further confuse things.
I suspect the manufactures are trying to mitigate the problems found in the 70s, but that's speculation & not 'Fact'.
I suspect it's a 'Lawyer' thing, like triggers that need a pry bar & safeties popping up in places they haven't traditionally been.
Mostly because I couldn't twist my head around the issue for reloading, and I've tried for quite a while.
I'm crystal clear on the machining/processes end of things,
This is one of those subjects with so many variables it's actually a little hard to grasp and cook down into one blanket statement.
Sorry if it ruffled your feathers, I'm just looking for some Go/NoGo lines you shouldn't cross.
-----------------
I'm with Clark, I got an 'AR-15 Upper, Generic' in a trade for some parts that had a chamber so tight nothing fit into it.
Bore scope showed a REALLY dull reamer, metal smearing, gouges, a bore that looked like it was cut with an old brick.
It's a really nice bar over the camp fire pit now.
Wasn't going to cut the chamber, then try and lap the bore out smooth for the $120 it takes for a new barrel...
------------------
TMD,
There are a bunch of 'In Between' chambers/reamers on the market, you have to be specific you want a STRICTLY SAAMI chamber reamer these days to get a strictly SAMMI specification throat.
Some barrel manufacturers have their own chambers that are 'In Between' you normally can't find the reamer on the open market. Proprietary, more or less.
Some have gone to the trouble of getting SAAMI recognition, like the Bill Wylde chamber (.223 Wylde), Some haven't.
I just a Geek from the country that casts/gauges chambers, and I rarely run in to a 'Strict' .223 Rem chamber or 'Strict' 5.56 chamber anymore unless it's on an older civilian rifle, or on a military barrel, almost everything is 'In Between' to further confuse things.
I suspect the manufactures are trying to mitigate the problems found in the 70s, but that's speculation & not 'Fact'.
I suspect it's a 'Lawyer' thing, like triggers that need a pry bar & safeties popping up in places they haven't traditionally been.
Lets look at Federals warning.
http://le.atk.com/downloads/technical_bulletins/223VS556.pdf
Lets check out some Federal 223 vs 5.56.
http://www.midwayusa.com/product/95...emington-55-grain-full-metal-jacket-boat-tail
Technical Information
Caliber: 223 Remington
Bullet Weight: 55 Grains
Bullet Style: Full Metal Jacket
Case Type: Brass
Ballistics Information:
Muzzle Velocity: 3240 fps
Muzzle Energy: 1282 ft. lbs.
http://www.midwayusa.com/product/95...to-55-grain-xm193-full-metal-jacket-boat-tail
Technical Information
Caliber: 5.56x45mm NATO
Bullet Weight: 55 Grains
Bullet Style: XM193 Full Metal Jacket Boat Tail
Case Type: Brass
Ballistics Information:
Muzzle Velocity: 3240 fps
Muzzle Energy: 1282 ft. lbs.
Same manufacturer (Federal) same bullet same velocity, to me that equates to Identical Pressures.
The 5.56 having less case capacity then the 223 has been disproven time and time again.
http://www.6mmbr.com/223rem.HTML
Scroll down to
.223 Rem Case Weight vs. Capacity
You will note that the 5.56 LC cases (Federal) have less weight and more capacity then the Federal 223 cases.
Lake City 06 Weight 92.0 Capacity 30.6
Federal Weight 96.3 Capacity 30.2
IMO, to many errors in the Federal Warning page.
http://le.atk.com/downloads/technical_bulletins/223VS556.pdf
Lets check out some Federal 223 vs 5.56.
http://www.midwayusa.com/product/95...emington-55-grain-full-metal-jacket-boat-tail
Technical Information
Caliber: 223 Remington
Bullet Weight: 55 Grains
Bullet Style: Full Metal Jacket
Case Type: Brass
Ballistics Information:
Muzzle Velocity: 3240 fps
Muzzle Energy: 1282 ft. lbs.
http://www.midwayusa.com/product/95...to-55-grain-xm193-full-metal-jacket-boat-tail
Technical Information
Caliber: 5.56x45mm NATO
Bullet Weight: 55 Grains
Bullet Style: XM193 Full Metal Jacket Boat Tail
Case Type: Brass
Ballistics Information:
Muzzle Velocity: 3240 fps
Muzzle Energy: 1282 ft. lbs.
Same manufacturer (Federal) same bullet same velocity, to me that equates to Identical Pressures.
The 5.56 having less case capacity then the 223 has been disproven time and time again.
http://www.6mmbr.com/223rem.HTML
Scroll down to
.223 Rem Case Weight vs. Capacity
You will note that the 5.56 LC cases (Federal) have less weight and more capacity then the Federal 223 cases.
Lake City 06 Weight 92.0 Capacity 30.6
Federal Weight 96.3 Capacity 30.2
IMO, to many errors in the Federal Warning page.
JeepHammer
Moderator
In 2012, according to the government,
Governmental and Military went to Exactly the same case as 'Civilian' .223 Rem.
Don't know what prompted that, other than the document stated a 'Ammunition Weight Reduction'.
I suspect it was two wars and homeland security buying up 2.3 billion rounds.
I can't see where a couple of grains qualifies as a significant weight reduction, but it's the government... Go figure.
They are shooting for a 10% weight reduction, which will mean poly cases,
Bad news for reloaders using military Once Fired cases.
I found some poly cases in the last batch of military brass I purchased, not a good sign...
Actually, I never had an issue with 'Case Weight' or 'Case Volume'.
Cases always held enough propellant for consistent .223 rounds,
Although I did separate the military cases for the semi-autos,
And used 'Civilian' cases in my bolt rifles.
I go through a LOT more ammo in the autoloaders, while the bolt rifles collect dust, and the cost reduction using military cases was attractive.
I recently tried a scale to separate civilian manufacture from military manufacture, and the scale couldn't reliably tell the difference,
Most of the military brass I have is current, post 2012, so that would make sense... If not be strict 'Fact', it goes along with what I'm seeing...
The fact that ATK/Federal took over Lake City might also have something to do with it...
Governmental and Military went to Exactly the same case as 'Civilian' .223 Rem.
Don't know what prompted that, other than the document stated a 'Ammunition Weight Reduction'.
I suspect it was two wars and homeland security buying up 2.3 billion rounds.
I can't see where a couple of grains qualifies as a significant weight reduction, but it's the government... Go figure.
They are shooting for a 10% weight reduction, which will mean poly cases,
Bad news for reloaders using military Once Fired cases.
I found some poly cases in the last batch of military brass I purchased, not a good sign...
Actually, I never had an issue with 'Case Weight' or 'Case Volume'.
Cases always held enough propellant for consistent .223 rounds,
Although I did separate the military cases for the semi-autos,
And used 'Civilian' cases in my bolt rifles.
I go through a LOT more ammo in the autoloaders, while the bolt rifles collect dust, and the cost reduction using military cases was attractive.
I recently tried a scale to separate civilian manufacture from military manufacture, and the scale couldn't reliably tell the difference,
Most of the military brass I have is current, post 2012, so that would make sense... If not be strict 'Fact', it goes along with what I'm seeing...
The fact that ATK/Federal took over Lake City might also have something to do with it...
JeepHammer said:
That's odd. That would make them heavier. Lake City 5.56 cases have generally as light or lighter than civilian cases since well before 2012. Look at the LC 06 in this article. 92 grains. Lightest cases among all measured, including a number of commercial brands.
Are you sure your source wasn't referring to 7.62 NATO? Those military cases really are heavier than commercial by as much as about 6%. When Federal developed the Mk316 mod.0 sniper ammo for the M24 sniper system, they used their own brass standards to get better accuracy. Lack of failures there may have prompted a change in military thinking.
Regarding the .223/5.56 pressure. Back when the copper crusher was king and M193 was the standard ball ammo, the pressure standards were:
M193/223 Rem
Military: 52,000 psi by copper crusher.
SAAMI: 52,000 CUP (same as psi by copper crusher, above)
Euro NATO: 3700 bar (53,664 psi) by copper crusher
CIP: 3700 bar (53,664 psi) by copper crusher
The slight difference in the NATO pressure will be due to their slightly different crusher geometry, rounding error, and possibly just normal variation in the mean value due to the fact copper crushers are not very precise instruments in the first place.
So, all through the Vietnam war and on through to the 80's, at least, the 5.56 and 223 pressures were all the same except for specialty ammo. M995 AP, for example, had a MAP (Maximum Average {peak} Pressure) of 50,250 psi.
And then the piezoelectric transducers came in and all that (relatively) uniform simplicity goes to pot.
First, our military started playing with transducers. Something went wrong with the equipment types. If you look at the specifications for M855 ammo you find it limits pressure to 55,000 psi, with three standard deviations not to exceed 61,000 psi. Reading copies of SCATO 5.56 for the time, the measurement is made using a "government approved pressure transducer". At the time they were experimenting with conformal transducers like the ones SAAMI uses. Since SAAMI adopted that same 55,000 psi value for their conformal pressure transducers, this seems likely. Today the military is using the Kistler 4206 transducers, same as Metric NATO and the later (2001 and on) documents describe that and have higher pressure limits. SAAMI, however, did not change.
And the metric folk across the pond took the reference ammo from the copper crusher days and tested it using those same Kistler transducers, NATO measuring at the case mouth and CIP at 25 mm (0.98") forward of the breech. Both came up with a standard of 430 MPa or 4300 bar. This converts to 62,366 psi. Today, that is the NATO pressure limit for 5.56 NATO, and it is the CIP limit for 223 Remington.
If you've been paying attention, you'll note that if you buy European 223 Remington ammunition, you are buying ammunition loaded with a 62,366 psi pressure limit by their measuring method. Norma, Lapua, Sellier & Bellot, Fiocchi, etc., and the Russian Wolf and Tulammo, as well. If you really think the nominally higher pressure limit of 5.56 NATO can harm your gun, stay away from foreign ammo. But before you let that scare you, look at your gun carefully. If the same basic action is made in .308 with the same barrel contour, you know that higher pressure with those thinner chamber walls and with the greater head cross-sectional area putting more thrust on the bolt face per psi is not going to damage the gun, so why should the same pressure in the smaller 223 case do it?
A note on test methods: with a little searching you will find things like the location of the pressure sample point at the case mouth or locating it mid-case results in about 2,000 psi difference in readings, worst case. Often there is almost no difference. There is a good measurement report on 223 vs. 5.56 mm in which Federal XM855 measures about 60,000 psi by strain gauge, and it is measured in two 5.56 chambers and one 223 chamber. The .223 chamber had the middle pressure value between the two 5.56 cases, so, again, the difference due to chambers is exaggerated. If you calculate the volume differences that the two chambers allow cases to expand to, you get very small percentage numbers. The more generous 5.56 chambers are really about ensuring smooth full-auto feed more than controlling pressure. The few specialty bullets that will make a significant difference in leade proximity are not commonly sold or used by civilians. The ball ammo shapes aren't particularly different from civilian shapes, including the bullet ogive. All the article authors trying to claim these factors I've just mentioned make big pressure differences are just searching for an explanation as to why the pressures are specified as different. I don't believe they are doing their homework on the differences in measuring systems.
As I've explained, the pressures weren't supposed to be different, originally. The different numbers were due to different pressure measuring methods at different points in history. Today, you can buy ammo loaded to a range of different pressures, apparently owing to some industry folk buying into the different numbers as real.
I am continuing to explore this topic a little further. I am putting another call into SAAMI, now that I have documented the military specs a little better, so see if they can add to the discussion.
JeepHammer
Moderator
Me Too!
I'm still confused...
The blurb I saw was a 10% weight reduction in 5.56, 7.62 & 50 Cal. ammo.
Didn't see a date for completion on that form. It was an internet copy, so I can't vouch for it's authenticity.
I'm still confused...
The blurb I saw was a 10% weight reduction in 5.56, 7.62 & 50 Cal. ammo.
Didn't see a date for completion on that form. It was an internet copy, so I can't vouch for it's authenticity.
I've got a theory that no one has proven wrong yet.
One of the problems that people don't like to talk about is the secondary pressure spike that comes from using too slow of a ball powder with too light of a projectile.
The 223 chamber exasperates the problem by having more initial resistance to the bullet meaning there is less effective volume for the secondary pressure spike. A looser lede or throat allows the bullet to be further down the bore when the secondary spike occurs, getting rid of the symptom caused by bad ammo.
People think that it's an ammo mismatch problem when it is in fact a bad ammo problem. By changing the chamber they are able to get rid of the high pressure symptoms and fall into a post hoc ergo propter hoc fallacy that it must be a chamber mismatch causing the pressure issues.
In fact the "popped primer" issue is almost always caused by a secondary pressure spike hitting when the bolt is unlocking or unlocked, allowing the brass to expand, cling to the walls of the chamber, and PUSH the primer out the back where it often falls into the trigger group. Then the pressure drops a bit, the brass springs back and shoots out under the residual pressure. If the pressure hit when the bolt was locked, you'd see pierced primers, not popped out primers.
Jimro
One of the problems that people don't like to talk about is the secondary pressure spike that comes from using too slow of a ball powder with too light of a projectile.
The 223 chamber exasperates the problem by having more initial resistance to the bullet meaning there is less effective volume for the secondary pressure spike. A looser lede or throat allows the bullet to be further down the bore when the secondary spike occurs, getting rid of the symptom caused by bad ammo.
People think that it's an ammo mismatch problem when it is in fact a bad ammo problem. By changing the chamber they are able to get rid of the high pressure symptoms and fall into a post hoc ergo propter hoc fallacy that it must be a chamber mismatch causing the pressure issues.
In fact the "popped primer" issue is almost always caused by a secondary pressure spike hitting when the bolt is unlocking or unlocked, allowing the brass to expand, cling to the walls of the chamber, and PUSH the primer out the back where it often falls into the trigger group. Then the pressure drops a bit, the brass springs back and shoots out under the residual pressure. If the pressure hit when the bolt was locked, you'd see pierced primers, not popped out primers.
Jimro
No doubt some issues occur with timing. A lot of domestic AR shooting, in particular, is with commercial ammo, some of which is loaded with very slow powder to meet the military velocity, but at the a lower peak pressure (part of the problem of buying into the numbers game). What is different is that the military tests not only peak pressure, but gas port pressure at a standard location and that has to be inside a tolerance range. The slow powders tend to have higher gas port pressure when used as I described, to there is a tendency for them to open the action fast. Additionally, when the same velocity is achieved by a slower powder than is usually used to achieve that velocity, the barrel time is longer, so that lengthens the gas impulse at that higher pressure. I'd have to examine how much, but it'll be something QuickLOAD can analyze well enough to proved some proportional result.
The following has over max load data . DO NOT use !
Unclenick:
If you do run some numbers through Quickloads . Can you plug in 55gr FMJ BT , 26.5gr IMR 4320 , CCI #400 primer , COAL 2.240 . I'm getting about 2900fps from a 16" barrel and it feels hotter then other loads I use . It feels like I'm way over gassed and was thinking some of that had to do with the slower powder . I know I'm over max charge weight as well but It's my most accurate load with that powder by far .
Unclenick:
If you do run some numbers through Quickloads . Can you plug in 55gr FMJ BT , 26.5gr IMR 4320 , CCI #400 primer , COAL 2.240 . I'm getting about 2900fps from a 16" barrel and it feels hotter then other loads I use . It feels like I'm way over gassed and was thinking some of that had to do with the slower powder . I know I'm over max charge weight as well but It's my most accurate load with that powder by far .
Metal god said:
QL is more accurate if the exact case capacity of a fired case is plugged in.
The default capacity for the 223 in QL is 28.8gr H20. I have not found any case with Capacity that small.
My LC brass has a case capacity averaging 30.5gr H20.
If you could supply your case capacity of a fired case that would be extremely helpful.
Also the exact bullet , Brand is also important.
CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.
Metal God,
My simple Excel file, based on Hodgdon's data for the 55 grain Speer Spire point, predicts 2902 fps from your barrel length (Hodgdon's is 24") and predicts 52,230 psi. Note that 26.5 grains is 0.4 grains over Hodgdon's maximum. Why there's is below the standard pressure limit, we don't know. It may be the powder gets squirrelly at higher pressures in this round.
QuickLOAD is in good agreement with the above when the case capacity is expanded from the default value to 29.4 grains. This is a low number. Most real cases seem to be closer to 30-30.5 grains case water overflow capacity.
I would suggest, if you are willing to go over published loads, that you should get the same velocity from 21.2 grains (21 grains is the listed maximum) of IMR 4198. It predicts a pressure of 49,761 CUP in the Excel file and very slightly lower psi in QuickLOAD than the 4320 load. It can do this because it burns much more completely in the short barrel. It fills the case to about 95%. It lowers the muzzle pressure about 10%, so gas port pressure will be down, too. It cuts 25% off your powder cost. Should be good to go, but work up toward it, just the same, for your lot of powder.
Metal God,
My simple Excel file, based on Hodgdon's data for the 55 grain Speer Spire point, predicts 2902 fps from your barrel length (Hodgdon's is 24") and predicts 52,230 psi. Note that 26.5 grains is 0.4 grains over Hodgdon's maximum. Why there's is below the standard pressure limit, we don't know. It may be the powder gets squirrelly at higher pressures in this round.
QuickLOAD is in good agreement with the above when the case capacity is expanded from the default value to 29.4 grains. This is a low number. Most real cases seem to be closer to 30-30.5 grains case water overflow capacity.
I would suggest, if you are willing to go over published loads, that you should get the same velocity from 21.2 grains (21 grains is the listed maximum) of IMR 4198. It predicts a pressure of 49,761 CUP in the Excel file and very slightly lower psi in QuickLOAD than the 4320 load. It can do this because it burns much more completely in the short barrel. It fills the case to about 95%. It lowers the muzzle pressure about 10%, so gas port pressure will be down, too. It cuts 25% off your powder cost. Should be good to go, but work up toward it, just the same, for your lot of powder.
Thanks UN
Most brass used is LC-11&12 mixed for that load . I have a large lot of that brass 600+ pieces that I cycle through . Problem with that is I use that brass for 2 other loads . I keep the brass separate per times loaded but not for each powder used . So no way to tell what powder was used last in a case . They all get placed into the same bin according to how many times they've been loaded .
The reason I went to 4320 was I wanted a powder that was not so commonly used . Over the last couple years I started to see that 4320 was available more then the more commonly used powders . I wanted at least one powder in my rotation that would be easier to get so that's why I use it . I normally would not even try that slow a powder with that light a bullet . In fact once I get more I'll be trying it with 62 & 69gr bullets to see how it does . On my burn rate chart 4198 is #70 and 4320 is #100 Not sure how accurate that is but anything close to that is a huge difference in my book .
Most brass used is LC-11&12 mixed for that load . I have a large lot of that brass 600+ pieces that I cycle through . Problem with that is I use that brass for 2 other loads . I keep the brass separate per times loaded but not for each powder used . So no way to tell what powder was used last in a case . They all get placed into the same bin according to how many times they've been loaded .
The reason I went to 4320 was I wanted a powder that was not so commonly used . Over the last couple years I started to see that 4320 was available more then the more commonly used powders . I wanted at least one powder in my rotation that would be easier to get so that's why I use it . I normally would not even try that slow a powder with that light a bullet . In fact once I get more I'll be trying it with 62 & 69gr bullets to see how it does . On my burn rate chart 4198 is #70 and 4320 is #100 Not sure how accurate that is but anything close to that is a huge difference in my book .
mehavey said:
How much over pressure?
The 223 has a SAAMI MAP of 55K psi. At what pressure would these loose pockets appear in the 223?
The 17 Remington has the same case head dimensions (.378), but it has a SAAMI MAP of 63K psi. At what psi would these loose pockets appear in the 17 Remington?
Would "overpressure" signs in the 223 appear just over 55K psi, but hold off with the 17 Remington until pressures exceeded 63K psi?
How does the brass case and the primers know what SAAMI has set for them and when they should show overpressure?
Overpressure becomes brass/manufacturer-dependent at the top end -- even within the same
cartridge/chamber -- and some brass gives the ghost quicker that others. (e.g. soft Federal)
The failsafe/weaklink canary is the case itself, and here's my rules of thumb:
- Blown primers (all the way out): 20-25,000(+) psi too high [Immediate Stop]
- Ejector marks: 15-20,000 psi too high [Immediate Stop]
- Loose pockets after 2-3 firings: 8-10,000 psi too high [drop charge 5-6%+]
- Loose pockets after 5 firings: 3-6,000 psi too high [drop 2-4%]
cartridge/chamber -- and some brass gives the ghost quicker that others. (e.g. soft Federal)
The failsafe/weaklink canary is the case itself, and here's my rules of thumb:
- Blown primers (all the way out): 20-25,000(+) psi too high [Immediate Stop]
- Ejector marks: 15-20,000 psi too high [Immediate Stop]
- Loose pockets after 2-3 firings: 8-10,000 psi too high [drop charge 5-6%+]
- Loose pockets after 5 firings: 3-6,000 psi too high [drop 2-4%]
Steve4102 said:
If cases were calibrated, there would be a fixed answer to that, But as recent posts about problems with the softness of Federal brass reveal, about the only thing the brass can tell you is when the pressure is too high for itself, as Mehavey described. Those numbers can be different not only within a lot of cases, but with some variation among the individual cases within the lot, as this Denton Bramwell article shows.
In general, I think if you measure the diameter of the head or the extractor groove, by the time it has expanded half a thousandth you are pretty definitely at higher pressure than that case is happy with, and you'd do best to back the load down 10% and work back up to, but don't exceed 5% less, checking again.
A more sensitive measure is the flash hole diameter. Mr. Guffey sent me a very handy tool for measuring this, but I don't know that he makes them any longer. If you get a 6/0 and a 5/0 taper pin, they cover the range of flash hole sizes, and you can measure how far they enter the flash hole to get and expansion indicator that way.