.223 Rem vs 5.56 x 45 NATO Accuracy

[ZeeOSix]

From what I've researched, a rifle chambered for 5.56 x 45 NATO can also safely shoot .223 Remington, but the accuracy when shooting .223 Rem may suffer. Has anyone verified this in their own rifle at the range?

Also, they say that if your rifle is chambered for only .223 Rem that using the 5.56 x 45 NATO round can be dangerous. My AR is chambered for the 5.56 x 45 NATO spec, but I'm wondering if accuracy will really be noticeably better using the NATO round vs. the .223 Rem.

 

[TheOnlySarge]

The most important difference between .223 and 5.56 chambers is the length of the throat (or leade) for each chamber. More specifically, the leade is located at the mouth of the barrel before the rifling occurs. Comparing the NATO and SAAMI regulations, the leade for 5.56 chambers is nearly twice as long as that of a .223 chamber (.162in to .085in, respectively). If a 5.56 round contacts the barrel rifling too early, it can cause pressure spikes (leading to malfunction, and potentially damage) in the chamber. This explains why it is safe to fire .223 through a 5.56 chamber, but not recommended to fire 5.56 through a .223 chamber.

 

[ZeeOSix]

^^^ Yes, but I've also read that firing .223 Rem in the 5.56 x 45 NATO chamber can result in less accuracy due to the length of the throat for each chamber.

I was just wondering by how much since I can't seem to find any tests results were someone used both rounds in the same gun at the range to get an accuracy comparison. I realize there are many factors that can effect on target accuracy, but wondering how much would be due to using .223 Rem in the NATO chambered rifle if all other factors were controlled.

 

[Vern_in_IL]

Obviously you need to spend some time at the range. With matched ammo, or careful reloads.

Record everything and get a MOA(Measure Of Accuracy), record everything. That will give you the best results.

I would not trust anyone else if you possibly might use this in a self defense situation.

Might need trigger work if you are not happy with the pull, so many variables!!

 

[Oro_O]

Originally Posted By: Vern_in_IL
Obviously you need to spend some time at the range. With matched ammo, or careful reloads.

Record everything and get a MOA(Measure Of Accuracy), record everything.


Before lecturing someone dismissively on what they should or should not do, spend some time learning about shooting terminology. That is not what that means.

ZeeOSix - in practical terms, unless you are shooting at a very competitve level with a floated barrel, etc., you are not going to see a quantifiable difference based on the lead between .223 and 5.56.

 

[ZeeOSix]

Originally Posted By: Or
ZeeOSix - in practical terms, unless you are shooting at a very competitve level with a floated barrel, etc., you are not going to see a quantifiable difference based on the lead between .223 and 5.56.


Thanks for that info. So this is what puzzles me. According to these drawings, there are not dimensional differences between the two rounds (unless info on wikapedia is wrong). I was under the impression that the NATO round was dimensionally different and that's why a rifle chambered for NATO had the longer throated chamber.

The only difference I see is the radius on the case where it necks down. All other dimensions are the same. Is it more of a chamber pressure thing vs. a chamber size thing - NATO round producing more chamber pressure?

Why is the NATO chamber sized differently if the rounds have the same exact dimensions?

.223 Rem

5.56 x 45 NATO

 

[RW1]

Oro, what are you referring to? I understood what Vern meant by MOA. Vern was not referring to Minute of Angle but Measure of Accuracy. I'm afraid I don't understand what your point is. Could you clarify?

 

[ZeeOSix]

Originally Posted By: RW1
Oro, what are you referring to? I understood what Vern meant by MOA. Vern was not referring to Minute of Angle but Measure of Accuracy. I'm afraid I don't understand what your point is. Could you clarify?


The acronym MOA means 'Minute of Angle' in the gun world, which is of course associated with accuracy. He just used the acronym wrong.

 

[RW1]

Okay, I've heard both terms in the high power rifle shooting arena.

 

[DuckRyder]

 

[Leo99]

I shoot both rounds with my AR and don't see any difference. If there is a difference, it's well beyond my ability to discern it.

Maybe what you read is referring to variability within the ammo. In other words, if you locked down your AR, your groups with 5.56 will be tighter than .223 due to tighter controls in the manufacturing of the 5.56 rounds. I'd call this more precise, not more accurate but as you can see above, people use terms to mean different things.

 

[billt460]

There isn't enough difference to worry about. I no longer segregate my 5.56 MM and .223 brass because there is no need to. Also, I have never heard of, or seen a .223 rifle damaged from shooting 5.56 MM ammunition in it..... Ever. Not even as much as a damaged extractor.

 

[ZeeOSix]

DuckRyder - good video, thanks.

So since both rounds are physically the same dimensions, it seems to boil down to the 5.56 x 45 NATO round can be loaded to a higher pressure (due to thicker brass I read) which could be unsafe in a rifle chambered solely for .223 Remington. I would think that also means that typically the NATO round it also a higher velocity round.

 

[CT8]

The 5.56 is a hotter round, the chamber pressure is much higher. Think of a +p load.

 

[BrocLuno]

I'm not a 223 shooter - more of 22-250 guy. But what I get from my 223 buddies is that the same powder charge is in a Nato and a Civ 223. But the brass is thicker near the base (to keep the head intact for auto-extraction) so the pressures are higher.

I don't know if anyone has blown up a rifle because of the difference... But I tend to think it's a bit more of an engineering issue, than a real world one for most rifles ...

 

[Ethan1]

The question is: are you a precise enough shooter to detect / care about tiny differences between .223 and 5.56?

I, for one, am not there yet

 

[Shannow]

My CZ527 being made in the same factory as the mil stuff has the NATO chambering...well at least I can seat a 63 gr military projectile completely out of a properly trimmed case and still not touch the rifling (boat-tail is still in, but not gripped).

Can't shoot mil stuff with the 1:12, but it will still do MOA with 60gr VMax punted as fast as I can with AR2206 (close to 3031).

 

[hatt]

Originally Posted By: ZeeOSix
My AR is chambered for the 5.56 x 45 NATO spec, but I'm wondering if accuracy will really be noticeably better using the NATO round vs. the .223 Rem.
What premium 5.56 ammo are you going to use? There isn't much selection. If you're shooting M193/M855 vs blaster .223 the chamber you have isn't going to matter much. Quality .223 will most likely out shoot the cheap M193/etc. The only way it's going to matter is if you have an accurate barrel and are comparing premium match 5.56 vs premium match .223.

 

[hatt]

Originally Posted By: Shannow
My CZ527 being made in the same factory as the mil stuff has the NATO chambering...well at least I can seat a 63 gr military projectile completely out of a properly trimmed case and still not touch the rifling (boat-tail is still in, but not gripped).

Can't shoot mil stuff with the 1:12, but it will still do MOA with 60gr VMax punted as fast as I can with AR2206 (close to 3031).
1:12 is perfect for M193.

 

[Shannow]

Oz use the 62 grain which goes through the target sideways at 300 yards.