5.56/.223 Accuracy

[j_san]

I have yet to chamber any 5.56 ammo into my 180B. I have only shot Factory .223. Just curious if any other AR shooters notice better accuracy with 5.56 in their rifles in this caliber?

 

[Scharfschütze]

My AR15 shoot way better with 5.56 than with .223. It loves the PMC M855. Wish I had more of it.

 

[j_san]

Im glad that you noticed. I think Im gonna try to grab a case and see what its like for myself. thanks

 

[Tuco Pike]

Is the AR-180b chambered in 5.56 or 223?

 

[Gailamir]

I think the AR-180b is chambered in .223. You should not be firing 5.56 mil ammo with this rifle.

 

[Cerendrad]

Where can one buy 5.56 nato in bulk?

 

[jfarrell]

if the rifle is a .223 and you shoot 5.56, you will eventually ruin the barrel as the pressures are much higher in nato rounds

 

[Throttle_monkey1]

I don't think it's the barrel that suffers. Isn't the higher pressure of 5.56 in a .223 chamber dangerous because of the headspacing?

 

[jazaman]

if your rifle has not been designed to shoot 5.56; you should only use .223..


im also curious as to where you can get 5.56 ammo; can't find it anywhere.

 

[Urban_Ops]

Really? Other than the odd box of .223 Black Hills ammo all I shoot through my rifles is 5.56.

 

[acrashb]

I don't think it's the barrel that suffers.

The whole system suffers. A respected gunsmith recently did a pressure trace test with 5.56 in a proper .223 chamber, average pressure was over 70000psi, which is basically a .223 proof load.

 

[fnrob]

I think the AR-180b is chambered in .223. You should not be firing 5.56 mil ammo with this rifle.

Nope, they're chambered in 5.56. Here's what the side of mine says:

 

[bluestratus]

neck concentricity on the pmc green tip is very good as good as some of the match ammo i have. but i cannot speak of consistency of the load and bullet

 

[easy]

The whole system suffers. A respected gunsmith recently did a pressure trace test with 5.56 in a proper .223 chamber, average pressure was over 70000psi, which is basically a .223 proof load.

I wonder which method did this smith used to derive to 70,000 psi before the primer gave up the ghost?

I think SAAMI uses a different method to measure chamber pressure with .223 rounds than the way 5.56 NATO rounds are measured.
Not sure exactly how SAAMI derives to their pressure measurements, but I seem to remember NATO measures 5.56 pressure at the case mouth with their test barrels.

The difference between the two methods equals to 20,000 psi more with 5.56, so if the SAAMI proof load for .223 is around 70,000 psi and 5.56 NATO rounds are considered safe at 58,000 psi, every 5.56 NATO round fired out of a .223 chamber will be pushing 78,000 psi. That's way over SAAMI's "proof load" of 70,000 psi. Sounds kind of risky to me. Or at least a lot more strain on the AR system than we're led to believe on the .223/5.56 differences by the errornet.

 

[j_san]

yeah mine's chambered in 5.56, thats why I was asking, but never the less; where could one grab a bulk case? Oh and Fnrob, I've read that the rifling is 1:9, is that correct?.

 

[fnrob]

yeah mine's chambered in 5.56, thats why I was asking, but never the less; where could one grab a bulk case? Oh and Fnrob, I've read that the rifling is 1:9, is that correct?.

I had to check the manual on that because I forgot, but yes, it says it's got a 1:9 rifling.

 

[acrashb]

I wonder which method did this smith used to derive to 70,000 psi before the primer gave up the ghost?

As noted "pressure trace" - http://www.shootingsoftware.com/pressure.htm - did the measurement.

My understanding is he used off-the-shelf XM193 in a 223 chamber. One assumes the primer died, but I don't have that information.

 

[acrashb]

Or at least a lot more strain on the AR system than we're led to believe on the .223/5.56 differences by the errornet.

At least. Lots of popped primers, leading to all sorts of interesting problems in AR trigger groups.

 

[Cerendrad]

Ok, Now that we are clear that 5.56 should not be shot out of .223 chambered rifles, where can someone with a 5.56 buy ammo (preferably in large quantities and heavy bullet weights)? I never see it for sale anywhere.

 

[acrashb]

preferably in large quantities and heavy bullet weights)?

Can't help you with where, but can with what. If you want "heavy bullet weights" ask for SS109 or M855 (essentially the same thing). That gets you the heavier 62gr bullet.