5.56 vs. .223 ----- again

[SecondsCount]

No
I think to many people put to much into “mil spec”. To my understanding in a nut shell, it means who was ever the cheapest got the bid.
I load my 223 to 5.56 pressure/data.
I was shooting milsurp 5.56 ammo in 223’s before this mythical problem came about, zero instances of any kind.

Exactly. It isn't like 5.56 ammo is that much hotter than 223. The worst that I have seen is heavy bolt lift.

 

[VA_XTC_Shooter]

Since you can't prove a negative, it's tough to say 100% 556 ammo in a 223 chamber will not blow up.

To muddy the waters, there are many variations of 223/556 chambers, each would have a different pressure with the same ammo.

I believe we all agree a longer freebore reduces pressure with same ammo.

The questions is how.much is the Delta? 2,000psi, 10,000psi?

The military specs 556 ammo to have 55000psi and arou d 3100fps. That is in a 556 nato chamber.

So, in a shorter freebore, the pressure would be higher, but how much, and would it be unsafe.

I'm not overly concerned with 556 ammo, but I just can't put out the blanket statement it is OK in a saami 223 chamber.

 

[rebs]

Not an answer but I load lake city cases with 223 load data for my bolt gun.
I have no need for any 5.56 ammo

 

[VA_XTC_Shooter]

https://www.luckygunner.com/labs/5-56-vs-223/

including strain qauge pressure testing results.

Lucky Gunner's test left a lot to be desired. He only showed ammo in one chamber, but did not use the same ammo in the opposite chamber for comparison. He did reference a study by Barnes, but I cannot find that study anywhere.
Barnes did do the same 223 ammo in both chambers and 556 ammo in both chambers for a comparison. As can be seen, the 556 ammo had higher pressure than 223 ammo in both chambers. The 556 ammo in the 223 chamber was higher than 55K, close to 60K. Not really an alarming pressure, considering most handloaders are usually at or around max listed pressure for their chamber.

I really would like to see the Barnes study to evaluate their process.

 

[dcali]

In every way that matters, they're the same thing. The slight difference in specs is just not significant enough to kaboom a gun. I've shot a .223 round loaded to significantly over 5.56 spec pressure in an AR (which is a relatively weak action) with a .223 chamber and nothing happened except the case stuck hard in the chamber. This is a non-issue propagated by internet forums. Factory 5.56 is safe in factory .223 chambers. If you do something stupid, that's on you, but mixing .223 and 5.56 isn't stupid.

 

[dcali]

Lucky Gunner's test left a lot to be desired. He only showed ammo in one chamber, but did not use the same ammo in the opposite chamber for comparison. He did reference a study by Barnes, but I cannot find that study anywhere.
Barnes did do the same 223 ammo in both chambers and 556 ammo in both chambers for a comparison. As can be seen, the 556 ammo had higher pressure than 223 ammo in both chambers. The 556 ammo in the 223 chamber was higher than 55K, close to 60K. Not really an alarming pressure, considering most handloaders are usually at or around max listed pressure for their chamber.

I really would like to see the Barnes study to evaluate their process.

I would agree - I don't doubt that he's seeing something and appreciate the thoroghness, but calibrating with factory ammo is iffy at best. His conclusions are also not consistent with his measurements. Even 60ksi of pressure (which i kind of doubt is actually the case) isn't going to blow anything up. The collective experience of hundreds of millions of rounds fired through tens of millions of guns proves it. The chambers just aren't that different.

 

[alf]

My latest AR barrel is from X-Caliber, and I specified their 223 Remington chamber with the SAAMI .025" freebore. I can touch the lands with 40 Ballistic Tip, 52 Bergers, & 53 Vmax, which I do using ACS magazines and their 2.300" mag length.

I would be jumping them at the "normal" 2.260" OAL, so I assume the factory 5.56 loads would not increase pressures little or any due to the Rem chamber, as they should still be off the lands as well.

 

[Hoser]

I shot many thousands of 5.56 through a plain jane commercial 223 chamber before the internet told me my gun would blow up.

 

[divingin]

A lot of the NATO (5.56x45mm) specs are here if you're interested:

5.56×45mm NATO - Wikipedia

en.wikipedia.org