Which should I order? I resize with an RCBS small-base .223 die. Thanks.

5.56 will give you more versatility/diversity in ammo choices and the differences in reloading are negligable.

Perry

What action?
What barrel twist?
What bullets are you expecting to use?

Larry Gibson

either - this 5.56vs 223 is a technofreaks bs. I know i know the difference, but i've shot enough thousands of rounds of military ammo of different makes in 223 chambers to call it bs

The last colt armorer school I went to last year the colt factory instructor says they are one in the same.

Go ahead and shoot both in the same rifle.

quote:

What action?
What barrel twist?
What bullets are you expecting to use?

Larry Gibson

Larry asked the right questions.
There is a difference in the lead in the throat, which will affect pressure. I can't say I've ever seen it make a difference with factory ammo, but I've seen differences with hand loads....

So Homebrew, what's your plan?

Order a 5.56 chamber and be done with it

From what I know, the throat in the 5.56 is a bit longer than the throat in the .223Rem. My question is: If I shoot mostly mil-surp 55-grain bullets in once-fired mil-surp cases -- but use the occasional 62-grain or even the 75-grain -- what should I buy? I am looking at a new upper for my AR. I like the standard A2 in the 20-inch barrel. I can choose 8 or 9 twist. I shoot nothin' but my reloads. I can chose carbon steel or stainless.

My buddy and I have several AR uppers. His .223 chambered heavy barrel shoots 1/2 MOA, where the 5.56mm uppers are close to 1 moa shooters. Of course the 5.56 uppers will handle an extra grain of powder in the hand loads. So If I wanted tigher groups, I'd go with the .223. If I wanted reliablility, I'd go 5.56

quote:

Originally posted by Antelope Sniper:
My buddy and I have several AR uppers. His .223 chambered heavy barrel shoots 1/2 MOA, where the 5.56mm uppers are close to 1 moa shooters. Of course the 5.56 uppers will handle an extra grain of powder in the hand loads. So If I wanted tighter groups, I'd go with the .223. If I wanted reliability, I'd go 5.56

That is the answer for which I was looking. I shall buy the .223Remington because all of my brass is trimmed to 1.753 inches and resized to where the head sets flush with the milled reference surface of the case comparator I use. There is never a chance the round will not chamber because it has not been resized correctly. I learned that lesson last Fall. Thanks, Antelope, for your considered reply.

quote:

That is the answer for which I was looking.

Anytime homebrewe. Us crazy mad scientist experiments have to stick together!

I am still confused. Are there two SAAMI cartidge dimensions, one for .223 and one for 5.56x45mm? I look in the major handloading manuals and they only show specs for .223 Remington. And then have loads, with the same dimensions, for "service rifle".

quote:

I am still confused. Are there two SAAMI cartidge dimensions, one for .223 and one for 5.56x45mm? I look in the major handloading manuals and they only show specs for .223 Remington. And then have loads, with the same dimensions, for "service rifle".

Yes, the throat is different.
.223 is the Saami standard
5.56x45mm is the military standard.
.223 Wilde is between the two.

quote:

Originally posted by sputster:
I am still confused. Are there two SAAMI cartidge dimensions, one for .223 and one for 5.56x45mm? I look in the major handloading manuals and they only show specs for .223 Remington. And then have loads, with the same dimensions, for "service rifle".

No, the cartridge dimensions are the same. It is the chamber differences, specifically the throats that Antelope is referring to.

Larry Gibson

Here's the money quote:



"The primary difference between .223 Remington and 5.56 x 45 mm is that .223 is loaded to lower pressures and velocities compared to 5.56 mm. .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 mm ammo will frequently cause over-pressure problems such as difficult extraction, flowing brass, or popped primers, but in extreme cases, could damage or destroy the rifle. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 mm "military" chamber specs, which contributes to the pressure issues.

While the 5.56 mm and .223 cartridges are very similar, they are not identical. Military cases are made from thicker brass than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the SAAMI location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56mm NATO, is around 78,000 psi ( ) tested in .223 Rem test barrels (SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56mm round fired is a proof load, very dangerous). The 5.56 mm chambering, known as a NATO or mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber[2] or the Armalite chamber, which are designed to handle both 5.56 mm and .223 equally well."

Standard 223 rem vs 556 or current deeper-throated 223 match versions- 556 has a very deep throat compared to the 233 rem. White Oak, CLE, Bushmaster Wylde etc are hybirds so HP shooters can run mag length 77s or less for rapid fire as well as long loaded 600 yd + single loaded fodder (greater than 2.260 OAL) and still stuff enough RL15 or Varget into them to get VLDs hopping along at near 2800+ fps (from a 20 inch barrel).

The 556 will (in my exp) not get that high of velocity with "safe" SAAMI handloads with heavy bullets as currently pulished by the component guys, mag length or long.

On the other hand, Check out Hornady's Superformance line- I noticed the 75 grn 223 makes (ADVERTIZED) about 2810 from a 24 inch barrel, while the 556 75 gren exceeded 2900 fs FROM A 20 INCH BARREL.

It, indeed, is a pressure equation.

556 is the safest way to go, BUT MAYBE NOT THE MOST ACCURATE.

I have a NM AR set up with a 1:9 20 in. 556 barrel that makes knot holes with 55-69 grain match loads, and nearly cleans the 600 target with 75 Hornady BTHPs over Varget. I won't publish the charge weight, but it did not exceed 2700 fs.

This rifle will not shoot VLD 75 grn AMAX worth spit (meaning 10 ring or less at any range), due to its rather slow twist rate and MV.

Best

Tigger;

The comment about 556 brass being thicker is not likley to be true. Weighing brass of all sorts, I found often the opposite. LC brass seems to weigh in around 93 grn, Win (the batch I have) is 2-3 grains heavier (meaning less capacity and potentially higher pressures, all else the same).

If one said "tougher" I'd buy it.

Federal GM (or any Fed 223 brass) is generally considered shoot once (factory) then recycle-too soft to handle any reloads. I have witnessed several case ruptures in ARs involving fed brass and stout but safe rl-15 or varget behind 77-90 grain bullets.

Have pics, but am not savvy enough (or patient enough) to post-I'll email to interested parties, however. Case head measured over .410 (should be nomially 373ish). Took a hammer and drift punch to with draw the AR BCG and a rod to drive out the failed brass. Scared the shooter much, the the AR held it toeghter-bent extracor was the only damage noted.

Best

In general mil-spec brass is thicker than commercial brass but some companies use the same brass for both, for example most Winchester is surplus/overrun. The "standard" answer is mil-spec has lower volume and to start with a lower starting load.

The differences between chambers is that the 5.56 is looser for easier extraction when dirty for full auto. Clymer has a 2 thousandths of an inch difference in the body, 7 ten thousandths at the shoulder, 1 thousandth at the mouth. Practically no differences.

If I were ordering a barrel I'd go with a Wylde chamber in a match barrel, stainless, and 1 in 8 twist.