If1HitU
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Very nice,beautiful looking rifle.
.223 vs .556 - Same Accuracy ?
- Thread starter jrehfuss
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sirgilligan
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This statement is only true with proper context.
The chamber is different for .223 and 5.56 NATO.
If you shoot 5.56 NATO ammo in a 5.56 NATO chamber the recommended maximum pressure is the 55,000 PSI (approximately).
If you shoot .223 REM in a .223 REM chamber the recommended maximum pressure is 55,000 PSI.
If you shoot .223 REM ammo that produces 55,000 PSI in a .223 REM chamber and you shoot it in a 5.56 chamber it will produce less pressure.
If you shoot 5.56 NATO ammo that produces 55,000 PSI in a 5.56 NATO chamber and you shoot it in a .223 REM chamber it will produce more pressure.
When this discussion arises remember that it is the chambers that are different.
sirgilligan
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Quality ammo is made more consistent. So, if you buy some bulk ammo versus target ammo there will be a difference.
I have a CZ 527. It has a 5.56 NATO chamber. It shoots everything great. I am not exaggerating and I have posted those results here before. I imagine, because I don't know, a quality barrel (every thing past the chamber and the lead) is more important than the differences between a .223 and 5.56 chamber.
Shoot different ammo, but I would expect your rifle to shoot everything well.
I wanna add, I did a ton of research on this very subject before I built my first AR. The only example I could find of using 5.56 in a .223 causing problems was exactly two different occasions. Both were outdoor carbine classes in the summer with no shade. It was a stacking issue. Short lead + hot day + hot rifle. It caused popped primers and stuck cases. I've been shooting in those conditions, and within 30 minutes these black rifles got too hot hold, without even firing them. Since that day I try to avoid said conditions, as such, my two older 5.56 barrels that are likely not to spec do not concern me. And the two recient builds are .223 Wylde, though I didn't seek out that chamber, it's what came with the barrel configuration I wanted( stainless, mid length, mid weight, fluted)
that's also how I found that reamer
that's also how I found that reamer
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My once fired 5.56 cases measure between 1.757" and 1.760". My Sierra loading manual lists case length for the 223 as 1.760".
This is assuming the 223 chamber is cut to SAAMI minimum dimensions. I suspect makers are cutting their 223 barrels with more generous throats and gentler leade angles.
sirgilligan
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Maybe, maybe not, I don't know what the proof load is for a .223 REM chamber, but I am willing to guess that it is much hotter than a 5.56 NATO standard round.
It has nothing to do with the proof round. It has to do with the freebore. If a barrel is marked "223 Remington" but the makers consider it safe for 5.56, it means makers are likely using a longer freebore. If so, the barrel does NOT conform to SAAMI specifications.
sirgilligan
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I do not understand your comment. I am saying that the proof round for .223 REM is probably hotter than a standard 5.56 round shot in a .223, and therefore a 5.56 round should not blow up in your face when shot from a .223. That is my conjecture.
I have no idea if they are cutting the chamber out of spec to be safer or not. I would hope that standards are met.
Ah, now I understand.
Any rifle has a fixed number of over pressure events it can handle before it lets go. Shooting 5.56 spec ammo in a SAAMI spec barrel has been shown to generate pressures of 70,000 psi or more. Makers can get around this problem by cutting the leades long and with shallow angles. However, a 223 chamber with a long leade no longer meets SAAMI specs. 223 chambers with longer leades are not dengerous, just no longer SAAMI chambers. So, when we are talking about generating excessive pressures from shooting 5.56 ammo in a 223 chamber, the conditions required to do so are a SAAMI chamber with the SAAMI specified throat and leade angle combined with 5.56 ammo loaded at the upper end of performance.
To the OP's original question of accuracy. I haven't found consistent unaccuracies between the two 5.56/.223
I have found major accuracy differences between brands, even with the same bullet weights and listed velocities.
Case in point last summer, mid Tactical season I was running out of reload 5.56 for my AR. Had to pick up some factory loads so I grabbed 3 brands. Shot 5, 5 shot groups at 100yds for testing. Below are the results along with 3 of my reloads. Factory are 55gr, reloads as listed (reloads were 1, 5 shot group).
Wolf 55gr 2.1"
AE 55gr 1.6"
PMC 55gr 3.7"
Handloads
55gr 1.0"
68gr .63"
75gr .86"
YRMV...
I have found major accuracy differences between brands, even with the same bullet weights and listed velocities.
Case in point last summer, mid Tactical season I was running out of reload 5.56 for my AR. Had to pick up some factory loads so I grabbed 3 brands. Shot 5, 5 shot groups at 100yds for testing. Below are the results along with 3 of my reloads. Factory are 55gr, reloads as listed (reloads were 1, 5 shot group).
Wolf 55gr 2.1"
AE 55gr 1.6"
PMC 55gr 3.7"
Handloads
55gr 1.0"
68gr .63"
75gr .86"
YRMV...
WestKentucky
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Not to mention that stinkin primer crimp
RecoilRob
Member
This is after resizing? If so.....I don't know what was up with the 5000 I processed a while back....but they were all way over and needed the crimped end removed to get them down to 1.750 trim length. Were your cases heavily crimped with a segmented type die? LC cases? It's always a crap-shoot with once-fired cases from the Military not knowing what the headspacing of the gun/s that shot them...but mine all sized down easily and the shoulders hadn't been blown forward excessively, it was just the crimp ended up being way over where the end of the case should have been. This is a good example of why we check things...eh?
The measurement was taken after being fired, not resized. Lake City cases, crimped primers, roll crimp at the mouth, manufactured by Federal, fired in my AR.
Your post made it sound like the cases were overly long before they were fired and just after being fired.
A lot of cases are overly long after being resized.
Your post made it sound like the cases were overly long before they were fired and just after being fired.
A lot of cases are overly long after being resized.
milemaker13
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I like this part. The internet sure has changed things up. Lol.
RecoilRob
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OK...first, my cases were a segmented collet type crimp...not a roll, so something is different here. Perhaps this has been changed in the last 10-15 years?
Second....what a case measures after firing is not important...the specs are for cases about to be fired hence meaning after resizing and prior to loading.
Many cases will grow with repeated firing, but I've never seen a single case grow by .020-.030" when fired in a chamber with good headspacing....and coincidentally be the exact same length as the crimped portion. This is what led (and still does) me to believe that these cases must have begun life over the nominal 1.560-1.570. Or...perhaps the actual crimping operation squished the brass out that much farther? I don't know...only offering to the masses what I've seen and the conclusion it led me to. Might be wrong on the conclusion but stand behind the observation.
Yep. But, I can't imagine firing a SAW without that primer crimp given what I know about them. The primer crimp removal for 5.56 is simply one more reason why I prefer .223 pre-fired brass to 5.56. I don't load to max where thicker brass might be useful. Compared with used 5.56 brass, I rarely see much problem in used .223 brass.
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