Seeing that my MP15 is a 556 NATO, does it matter as to accuracy between the 223 and the 556 ammo?

Also is the 556 more powerful than the 223?

Yeah, I'm new to the AR15.

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_It was love at first shot_

5.56 operates at a higher pressure than .223. Point of impact will be different because of velocity difference. So, yes, 5.56 is "hotter".

I get the most accurate load when loading closer to .223 levels. I load closer 5.56 levels for hunting loads, although not as accurate, they do produce a little more fps for more energy on target.

Just to confuse the issue slightly, 5.56mm has a higher pressure limit than .223 by about 7,000 psig. This is a result of the DOD chronographing small arms ammunition at 78 feet instead of the SAAMI 15 feet. [Why? Because that's how it was done waaaaaay back when.]. The higher pressure limit was necessary to meet military velocity specs.

Just because 5.56mm can be loaded to higher pressures doesn't mean it actually is. There has been a lot of development work on smokeless powder since the 5.56mm was developed, classified and adopted roughly 50 years ago. It may be possible to develop those velocities at lower pressures now. Ammo companies generally load to a velocity specification at whatever acceptable pressures are required.

OK, having taken care of background, 5.56mm ammunition may be 100 fps or so faster than .223 with the same bullet weight in the same barrel. That's not really enough difference to worry about with respect to power-however you may want to determine that.

.223 should have an accuracy edge. I'm not sure the AR platform will make that noticable.

The accuracy is dependent on the caliber the chamber is reamed. The leade is different between a 5.56 and 2.23 chamber.

5.56 chamber = 5.56 or .223. The leade difference will be a contributing factor to the accuracy equation when shooting .223 from a 5.56 barrel.

The biggest factor that affects accuracy is the skill and ability of the nut behind the trigger.

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-John

LOL, the nut behind the trigger.

I just picked up two 30 rnd boxes of ZQI 556 62g brass but it didn't say NATO though. A look at their site says 55K max psi.

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_It was love at first shot_

To me difference is price, .223 is cheaper and I am fine shooting with it. Freedomunition makes great .223 rounds with cheap $5 shipping last week. I am very accurate with this rifle and .223, nothing to improve, so 5.56 would be waste of $.

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Guns ...

I agree with JPes in that the accuracy is more about the chamber than the cartridge. A 5.56 round will be more accurate than a .223 round in a 5.56 chamber. However, the .223 chamber tends to be more accurate overall. Of course you should never fire a 5.56 in a .223 chamber.

Now, accuracy and precision are two different things. Check out this pic:


What we all want is both accuracy and precision. However, for the way I use an AR, I'm more concerned with accuracy. Why? Well, a little spread doesn't affect the type of hits I'm after. A group like the "High Accuracy Low Precision" target makes me smile. To a bench rest shooter nothing short of the "High Accuracy High Precision" is acceptable.

What kind of shooting will you be doing?

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Interesting chart. In my case I have low accuracy high precision with flyers. The flyers could be me though.

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_It was love at first shot_

On a tangent that is ammo related that affects rifle performance...

On several forums you'll see people obsession about the ejection pattern of their AR-15. Is it at the perfect ejection O'Clock position?



Some less than bright bulbs do not take into account...

1. 5.56 power > .223 power. The ejection pattern will evidence this. They'll freak out that their 5.56 chambered rifle is weak cycling .223. They'll make changes to this that and the other to get perfect ejection. They'll then shoot some 5.56 and freak out that their ejection pattern is off. IMO, as long as the rifle ejects the spent round, cycles the bolt enough to strip off the next round in the mag it's good to go.

2. Most consumer AR-15's are intentionally overgassed: more combustion gas pressure than is mil-spec. We as civilians do not have access to unlimited, free, single source uniform ammo to which we can tune our rifles. We have to put up with a variety of ammo, 223 and 5.56, from various manufacturers. Construction details, projectile differences, charge weight, propellant differences are different from manufacturer to manufacturer, production run to production run. A little intentional overgassing is a good thing. It ensures that the rifle will cycle a wide variety of off the shelf consumer ammo.

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-John

This is just my opinion...

Barring any obvious or hidden defect in the rifle, equipment is about 5% of the precision & accuracy equation. The nut behind the trigger is the other 95%.

First and foremost, pick the right tool for the job. If you're going after bench-rest precision, then buy a bolt action rifle or build a super tight clearance match grade everything 24" barrel, free float AR. Pop some premium glass on it. Break it in using the ridiculous shoot once, clean, repeat 20 times. Shoot 5 times, clean, repeat 5 times....

Second, precision and accuracy is dependent on the consistent application of the fundamentals of marksmanship. Lock your body into the rifle the same way every time. Press the trigger the same way every time. Be consistent in everything you do.

Third, don't do obviously stupid things that will adversely affect your potential for accuracy. Loaded up on caffeine before a range trip? Are you on any prescription meds that affect your physical abilities or perception? When was the last time you had your vision checked? Is your rifle well maintained.

Because of circumstance, I am primarily a pistol shooter. I am an OK rifle shooter. Most of the time, I'm limited to 100 yards. On few occasions, I can shoot longer distances. That being said:

14.5" home built AR-15. Standard combat trigger. Standard carbine buffer, carbine BCG, chopped A2 rear sight. 1:9 CMV (not chrome lined) barrel Pictured below at that time.



I put this together for about $575-ish. That tells you that this rifle wasn't built using top-shelf anything.

Shooting on a range supplied mandatory horrible plastic rest off a wobbly wood bench, using cheap-o steel case, Russian manufacture, bi-metal jacketed 55gr TulAmmo. 100 yards.

Real world, fast pace fire.


Slowing down. Locking in my body position.



Slowing down. Locking in my body position, locking in my trigger hand & press.



Making sure I'm locked in place. Concentrating on shooting at my respiratory pause. God smiles upon me...



Practice is essential. I don't mean blasting away carelessly or half-hearted. What I mean by practice is meaningful, constructive, practice. The hardest part for me is to be brutally honest with myself. I will make the mistake of thinking I'm better than I actually am and lie to myself. I'll shoot, get bad results, get frustrated and blame everything but me. I have to kick myself in the keister, pause, and figure out what I'm doing wrong. I'll ask someone to eyeball my technique and let me know what they see so I can fix it.



I shot that target with a rather poopy quality AR-15. You have a M&P 15. It's like comparing a Yugo to a Lexus. Just get some meaningful, constructive practice in. Everything will come together.

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-John

This is an interesting observation. I might put the percentages differently, but the result is the same.

However, if you want to eek out that last bit of precision from your rifle, you absolutely must evaluate the gun. This can only be done with the human element removed. Shoot off a rest that holds the rifle without help from you. The only thing you do is press the trigger. This is the absolute best the rifle can be. Every other type of rest has some human influence.

Once the precision of the equipment is determined, then you can trouble shoot the shooter's performance.

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Freedom isn't free.

One of the problems with shooting the AR from a bench is that it is difficult to obtain a really stable shooting hand position without fussing a lot. Can be done, but it's not conventional bench position.

While it's off topic, about the over gassed contention........ We've got Colt M4s with all the milspec parts that with M193 ball produce ejection patterns that, by that diagram above, show them to be over gassed. I strongly suspect that diagram is for full size rifles with appropriate gas systems.

Having said that, the AR system is over gassed by design to ensure operation in the mud, blood and grit of real world conditions while dirty/fouled. Going to the M4, the pressures in the carrier go up even higher, by 50% from one authority. Yes, the gas port is smaller. That causes a longer time interval to build up the pressure necessary to operate the system, it doesn't reduce the pressure.

You know, I never thought about ejection patterns. I know they can indicate trouble in other guns. In hand guns, it doesn't really matter where it throws them, just that they are consistent.

My AR throws the casings in the red zone from JPes' chart (12:00-3:00). Does that mean my gun is malfunctioning?

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Freedom isn't free.

With handgun, a weak/worn recoil spring can make the shells come at you or even hit you.

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_It was love at first shot_

First off, you'll note JPes offers the chart as an example of obsession over minute details.

Having noted that, at least one authoritative source suggests that ejection in the 1:30-2 o'clock area is normal if you're firing M193/M855.ammunition. Our collective experience over decades with weapons maintained by certified armorers seems to bear that out. [IIRC, 4-4:30 suggests sluggish ejection, if you've screwed with heavier buffers, go lighter.] Remember that the ARs have shell deflectors, so you're not seeing a pure ejection path.

Probably the best advice I've heard/read on this is if your piece is ejecting consistently and has no actual malfunctions (failures to feed/extract), don't worry about where the brass lands. Also recall that the AR is a military design. Getting the empty out and a new round chambered is a priority over theoretical quibbles (by people who didn't design the weapon system-neither did I by the way, but I listen when the folks who make them speak/write) over ejection patterns. Reliable function over a wide range of conditions is why the (rifle length) system was overgassed from the initial design. FWIW, I've been using the system off and on since about 1970 and have never worried over where the empties land. So long as they clear the weapon, I don't care where they go....until I need to pick up brass.

If you have a lot of rounds through the weapon, checking the action spring free length and extractor, extractor spring and plug are suggested as preventive maintenance. If they're OK and you're in the mood and have the bucks, you might play with buffers (H/H1 or H2) if you're really bored and concerned over where your brass lands. However, these might cause ejection issues with certain ammunition with different pressures/pressure curves than the mil-spec ball noted above.

It does belatedly dawn upon me that if you're burning .223 rounds in an AR, that chart is probably pretty close.

Unless someone can document significant differences in gas port size for similar barrel lengths, I rather doubt that there's any significant difference in "gassing" between civilian and mil-spec firearms. As noted previously, the system was intentionally overgassed from the original design. Pressure beyond what's necessary to operate the weapon is vented when the bolt unlocks and the gas block unmasks the gas tube. If the weapon is sluggish, the pressure builds until it unlocks. If it's really sluggish, the bullet exiting the barrel vents the pressure, resulting in extraction/ejection failure.

Note: H2 buffers are used in full auto weapons to control the cyclic rate. They might have some value if you have a sound suppressor on a semi. Otherwise, save your bucks.

Boy, the topic done drifted.

Bingo.

Yup. It's been a while since the last rabbit hole and I missed it. LOL

The new guys would have asked sooner or later, so might as well get it over with .

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-John

I guess I should have included a in my last post. I wasn't really serious about it. I'm a firm believer that if your gun cycles and fires, everything else is superfluous.

I actually like where my gun ejects. It's very consistent. I could probably put a 5 gallon bucket at about 2 o'clock and not have to pick up any brass.

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Freedom isn't free.