223 vs 5.56 ?
- Thread starter rebs
- Start date
Marco Califo
New member
No. That is not correct. The case dimensions are one and the same.
The answer still applies. Your question was answered.
condor bravo
New member
Well the answer depends on the gun the rounds were fired in as indicated in the above responses. Due to chamber difference, a round fired in a .223 rem bolt gun will normally result in more pressure than the same round fired in an AR type rifle. Perhaps the question that is really being asked relates to the difference between .223 rem commercial and 5.56 mm ammunition produced for the military, their specifics being somewhat different, and can or should 5.56 mm military rounds be fired in a standard sporter bolt .223 rem rifle or AR type. Yes of course they can, pressures will vary and usually will be increased in commercially dimensioned chambers compared to pressures generated in military 5.56 mm rifles. But most will still consider it safe to fire the military rounds, although loaded somewhat hotter than most commercial .223s, in standard rifles. There have never been any official reports to the contrary.
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A couple interesting points about 223/556 comes in terms of pressure and throats. 223 max pressure is 55kpsi and 556 is 60kpsi. 223 chamber throat is shorter than the longer 556 chamber throat. If you shoot a 223 in a 223 chamber, you have "X" pressure. Shoot the same 223 in a 556 chamber and you have "X-" pressure. If the 223 is near the start levels, you could experience ar cycle issues. Taking a higher pressure 556 round in a 223 chamber w/ the shorter throat can cause "X+" pressures. It's a who knows what in the start to max powder range when it becomes dangerous. Compound that w/ missing the trim needs, then it can really be a booger. Best to follow the barrel stamp and manufactures recommendations. Call the rifles manufacture tech supt.
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Not sure the exact focus of your question as it is broad in nature.
If you work up a 223 load for accuracy, it will be different than an accuracy work up for 556. They will perform differently to one degree or another or they may be very close in different aspects of performance categories.
Stating a load work up for a caliber is broad natured in itself as there are lots of variables. To name just a few, FB bullets vs BT bullets vs under 300 over 300, barrel harmonics, heat, purpose of the specific loads, etc.
I'd just work up your 223 and 556 loads separately from start watching pressure signs and plan on hitting the target at different locations. If you use a scope, you can adjust the turret accordingly between the two.
Be prepared that mixing head stamps will be frustrating if you have ocd expecting perfection, especially when dialing in your scope. Stay way away from max if mixing headstamps as todays range brass is not tomorrows range brass.
Examine each piece of once fired brass prior to doing anything else w/ said brass.
Really pay attention to max trim length and use a headspace gauge. When running them thru a head space gauge, that is an excellent time to examine each piece of brass.
I like to use dummy rounds first in gauges and chambers to make sure all is as expected before I make live rounds.
Decide your expectations for what you are planning on doing w/ your ar-15. I have one ar that gets Norma treatment and another ar that gets budget bullets in mixed headstamped cases and use the powder that is most readily available in my area and have fun.
This is a generic over view response and you can refine it as you go. Don't just take a response and immediately go w/ it. Let is set a few days in case of a typing error and others find it and offer up corrections.
If you work up a 223 load for accuracy, it will be different than an accuracy work up for 556. They will perform differently to one degree or another or they may be very close in different aspects of performance categories.
Stating a load work up for a caliber is broad natured in itself as there are lots of variables. To name just a few, FB bullets vs BT bullets vs under 300 over 300, barrel harmonics, heat, purpose of the specific loads, etc.
I'd just work up your 223 and 556 loads separately from start watching pressure signs and plan on hitting the target at different locations. If you use a scope, you can adjust the turret accordingly between the two.
Be prepared that mixing head stamps will be frustrating if you have ocd expecting perfection, especially when dialing in your scope. Stay way away from max if mixing headstamps as todays range brass is not tomorrows range brass.
Examine each piece of once fired brass prior to doing anything else w/ said brass.
Really pay attention to max trim length and use a headspace gauge. When running them thru a head space gauge, that is an excellent time to examine each piece of brass.
I like to use dummy rounds first in gauges and chambers to make sure all is as expected before I make live rounds.
Decide your expectations for what you are planning on doing w/ your ar-15. I have one ar that gets Norma treatment and another ar that gets budget bullets in mixed headstamped cases and use the powder that is most readily available in my area and have fun.
This is a generic over view response and you can refine it as you go. Don't just take a response and immediately go w/ it. Let is set a few days in case of a typing error and others find it and offer up corrections.
I love to answer this question because it's the opposite of what one may think . No it is not the same ,
what ??? Yep that's right I said it . But how can this be ?? Simple , The 5.56 is not loaded to match quality standards and if you get 2 moa ( 2 inch group at 100yds ) out of it you're doing pretty good . How ever there are many 223 Rem match quality commercial rounds out there that will shoot circles around any 5.56 NATO round . Fed gold metal match and Blackhills match ammo's come to mind when talking accurate 223 ammo . These tend to shoot very accurately regardless of firearm used or chamber shot in . That said match ammo is expensive and you often get what you pay for . If you're asking does cheap 223 rem ammo shoot the same as 5.56 NATO . I think I'd say yes . Generally when comparing cheaper ammo you really need to see what your firearm will shoot better . I have a 223 Wylde chamber 1-8 twist that shoots green tip ammo better then 55gr Fed AE . How ever my 5.56 chamber with 1-9 twist shoots the AE a little better . It just depends on what your rifle likes better .
For some ballistics comparisons between 223 and 556, use Hornady's ballistic calculator w/ their bullets and plug in some fps, etc. Vortex has a nice LRBC that you can use after you make a userid and pwd. There are apps out there that will give you great tables but they cost. There are some hunting pages that can give you some comparisons, but I am not a hunter and can't recommend any as I don't know which is correct or speculation wind.
rebs said:
Until you get to benchrest or varmint accuracy levels they are not distinguishable. Once you do get to the highest accuracy levels, some brands are made more consistently than others, same as with any other chambering. But not counting that, they are the same.
qrz said:
Original spec M193 is 52,000 psi (by copper crusher; so same as SAAMI CUP unit). Original SAAMI spec for 223 Rem is also 52,000 CUP. And why wouldn't they be the same? Remington was involved in developing the round and simply copied it with a new name for civilian use.
Then the trouble started. The NATO countries got reference loads from the U.S., but they used a different measuring apparatus. Their apparatus was a metric copper crusher with slightly different size pistons and they got a projected peak number of 3,700 Bar, or about 53,200 psi from those same reference loads that the US got 52,000 psi from. The CIP copied NATO's number for European-made 223 Remington as their copper crushers were closer to the NATO type. Then NATO started moving to Kistler piezoelectric transducers which measured shared reference loads to project a peak of 4,300 Bar, or about 62,366 psi. So CIP copied that and loads their 223 Remington to 62,366 psi, but using an apparatus closer to NATO's (also a channel transducer reading through a drilled hole in the case, except the NATO EPVAT protocol measures through a hole into the barrel just in front of the case mouth, while CIP uses one through the case 25 mm forward of the head; but the difference would only be perhaps a couple of thousand psi, absolute, and zero if they calibrate to the same reference loads).
At the same time (80's and 90's) SAAMI had also adopted a piezo transducer apparatus, but not the drilled hole type Kistler channel transducer, but rather the conformal piezo transducers that reads over top of the unbroken brass case with a piston tip machined to match the chamber wall, and positioned just below the shoulder and which has different mass and response than the European type. Using the same reference load that gives the Europeans 62,366 psi, they got a peak of 55,000 psi. Why? Different apparatus with different limitations and error sources.
Then there is the U.S. military. If you look at SCATP specs from the 80's they refer to an "approved" type piezo transducer for the newer M855 and related rounds. M855 was rated at 55,000 psi by copper crusher, and they were getting numbers closer to 60,000 psi from them on the transducer. Later they went to the Kistler transducers to match NATO and issued the higher pressure numbers for them. Then in 2012, I understand ATK revised SCATP 5.56 and switched them to the SAAMI type conformal transducer for compatibility with commercial sources.
All this has caused a lot of confusion, as you might imagine. Also, the conformal pressure transducers seem to have improved and the difference from the readings they get on the European style transducers seems to have shrunk, as one Australian study shows. The difference now is mainly at very low pressures where, as you might imagine, the brass has more effect on the percent of the pressure applied to the transducer. One board member asked Federal what they load 5.56 to and they answered about 58,000 psi, which I suspect is taking the slightly warmer 55,000 CUP M855 load and measuring it on the conformal pressure transducer.
In the meanwhile, if you buy S&B or RWS or Norma or Lapua loaded 223 Remington ammunition, you are buying ammo loaded to the same peak pressure spec as 5.56 NATO is loaded to in Europe. At least, it's the same as for 55 grain ball ammo. If it hasn't blown anything up (and it hasn't) you don't need to worry about the pressure difference other than that the more generous NATO chambers may lower the pressure a couple thousand psi as compared to a tight match 223 chamber. But that's less than normal variation in pressure during testing, and actual ammo is seldom all the way exactly to peak anyway. I wouldn't fret about it.
The only glaring discrepancy I've seen is that Western powders has a separate list of loads for 62,366 psi. But the powder charge is not the same as their 55,000 psi loads. This is because, and I called their tech to verify it, they are using a conformal pressure transducer to measure that higher number, and not the European type transducer they should use for that number (I think; but recall the Australian study and it could be the 55,000 psi numbers are now a false low on current production apparatus). Anyway, the bottom line is, the same instrument used to limit to 55,000 psi should not be used to set a 62,366 psi limit as if it were a completely separate number. Only one of those numbers will match original developed load performance when measured on the same apparatus.
I agree, you hit it on the head. There is a lot of confusion on psi, cup, etc. Even the experts argue. Next year another engineer will come up w/ something else. I throw it in the "relative gain" department and use as a ball park number for cautious comparisons. Kind of like carbon dating. It's all grossly in error, but it's a common standard to reference from.
My Bushmaster V-match AR15 heavy barrel has some kind of NATO chamber.
If I put 75 gr bullets barely engaged in the case mouth, WAY too long for an AR15 magazine, the bullet still cannot reach the lands.
1.05 or 1.1" groups are possible with a few of my AR15s with 55 gr Vmax seated as long as will fit in the magazine.
Then I ordered a custom 223 reamer with the throat 0.050" shorter than SAAMI. Now if I put a 50 year old 22 rimfire barrel on a 100 year old military Mauser action, I can get sub moa on the first group of 35 gr Vmax.
Good 223 bolt actions I build can get several sub 0.5 moa on the first target.
To me a 556 is the opposite of being short sheeted. It is being a victim of too far to the lands.
If I put 75 gr bullets barely engaged in the case mouth, WAY too long for an AR15 magazine, the bullet still cannot reach the lands.
1.05 or 1.1" groups are possible with a few of my AR15s with 55 gr Vmax seated as long as will fit in the magazine.
Then I ordered a custom 223 reamer with the throat 0.050" shorter than SAAMI. Now if I put a 50 year old 22 rimfire barrel on a 100 year old military Mauser action, I can get sub moa on the first group of 35 gr Vmax.
Good 223 bolt actions I build can get several sub 0.5 moa on the first target.
To me a 556 is the opposite of being short sheeted. It is being a victim of too far to the lands.
Marco Califo
New member
Yes, you must use only 5.56mm dies when using 5.56 loading data. Safety first!
Marco Califo
New member
Mine all say 223. I have never seen 5.56 dies. So, I do not use 5.56 data.