Check the stampings on the BARREL.
Rock River Arms is known for using the Wylde chamber in their varmint rifles.
Posted on 02/21/2011 7:37:41 PM PST by neverdem
Is firing a 5.56 NATO cartridge in your .223 Remington chambered AR15 dangerous? Or do Internet forum-ninjas and ammunition companies selling you commercial ammo instead of surplus overstate the dangers? Believe it or not, a real danger exists, and some gun owners who think they are doing the right thing may not be safe.
The Cartridges
The .223 Remington and 5.56x45 NATO cartridges are very similar, and externally appear the same. But there are some differences that lie beneath the surface.
The 5.56 case has thicker walls to handle higher pressures, meaning the interior volume of the case is smaller than that of a .223. This will alter the loading data used when reloading 5.56 brass to .223 specs.
Some 5.56 loads have a slightly longer overall length than commercial .223 loads.
The Chambers
The significant difference between the .223 Rem and 5.56 NATO lies in the rifles, rather than the cartridges themselves. Both the .223 and 5.56 rounds will chamber in rifles designed for either cartridge, but the critical component, leade, will be different in each rifle.
The leade is the area of the barrel in front of the chamber prior to where the rifling begins. This is where the loaded bullet is located when a cartridge is chambered. The leade is frequently called the “throat.”
On a .223 Remington spec rifle, the leade will be 0.085”. This is the standard described by the Sporting Arms and Ammunition Manufacturers’ Institute, Inc. (SAAMI). The leade in a 5.56 NATO spec rifle is 0.162”, or almost double the leade of the .223 rifle.
A shorter leade in a SAAMI spec rifle creates a situation where the bullet in a 5.56 NATO round, when chambered, can contact the rifling prior to being fired. By having contact with the rifling prematurely (at the moment of firing), chamber pressure can be dramatically increased, creating the danger of a ruptured case or other cartridge/gun failure.
The reverse situation, a .223 Rem round in a 5.56 NATO gun, isn’t dangerous. The leade is longer, so a slight loss in velocity and accuracy may be experienced, but there is not a danger of increased pressures and subsequent catastrophic failure.
How serious is the danger of firing 5.56 ammo in .223 guns? Dangerous enough that the SAAMI lists 5.56 military ammo as being not for use in .223 firearms in the technical data sheet titled “Unsafe Firearm-Ammunition Combinations.”
ATK, the parent company of ammunition manufacturers Federal Cartridge Company and Speer, published a bulletin entitled “The Difference Between 223 Rem and 5.56 Military Cartridges.” In this bulletin, ATK stated using 5.56 ammo in a .223 rifle could result in “…primer pocket gas leaks, blown cartridge case heads, and gun functioning issues.”
However, the danger may be lower than SAAMI or ATK suggest. In Technical Note #74 from ArmaLite, the company states “millions of rounds of NATO ammunition have been fired safely in Eagle Arms and ArmaLite’s® SAAMI chambers over the past 22 years,” and they have not had any catastrophic failures.
According to ArmaLite:
“Occasionally a non-standard round (of generally imported) ammunition will fit too tightly in the leade, and resistance to early bullet movement can cause elevated chamber pressures. These pressures are revealed by overly flattened primers or by powder stains around the primer that reveal leaking gasses.”
What Do You Have?
So, if you own a rifle chambered for the .223 for 5.56, do you know for which caliber it is really chambered?
Many match rifles are chambered in .223 Remington (SAAMI specs) for tighter tolerances, and theoretically better accuracy.
Many of the AR-15’s currently sold on the market are made for the 5.56 NATO cartridge. If you own one of these, you should be fine with any .223 or 5.56 ammunition.
However, ATK dropped this bomb in the bulletin on the .223/5.56:
“It is our understanding that commercially available AR15’s and M16’s – although some are stamped 5.56 Rem on the receiver – are manufactured with .223 chambers.”
So, even if your AR is stamped 5.56, is it really? Check your owner’s manual or call the company directly and make sure you get an answer you feel comfortable with.
As if the confusion regarding the .223 vs 5.56 chambers wasn’t enough, there is a third possibility in the mix, that is being used by at least one major manufacturer. The .223 Wylde chamber is a modified SAAMI-spec .223 chamber that allows for the safe use of 5.56 NATO rounds, but maintains tighter tolerances for better accuracy.
Yeah, yeah… What’s the bottom line?
Here’s the bottom line. If you want to follow the safest possible course, always shoot .223 Remington ammunition. The .223 Rem cartridge will safely shoot in any rifle chambered for the .223 or 5.56.
If you want to shoot 5.56 NATO rounds, make sure you have a rifle designed for the 5.56 military cartridge. Shooting 5.56 in a normal .223 Rem rifle can result in bad things.
Even better:
Mosin-Nagant -> 7.62x54R caliber.
My Remington bolt action “Police Special” has a
.308 chamber with a tight throat. You can’t
safely shoot a 7.62x51 NATO in it. There are
headspacing issues between the two specs.
Check the stampings on the BARREL.
Rock River Arms is known for using the Wylde chamber in their varmint rifles.
I agree, and was also aware of the accuracy issue. I bought this weapon for a training class in order to be comfortable and capable of “running the gun” should a serious situation arise.
Pretty simple, just trim your cases to specification to be sure you have no head space problems and work your loads up before trying to go for maximum velocity and watch for pressure problems before they occur. You can also check for case internal volume by measuring before you reload your cases to look for case wall thickness affects before setting up your specific load. I have found that the commercial Winchester brass loads pretty much the same as their military brass and the same as Lake City brass. Stay away from the Federal brass.
Oh, yeah. Gotta love those Mosins! I'm down to only 5 of them, because friends keep buying them from me.
I think they're too lazy to clean the cosmo off, so they go for mine. LOL.
Thanks for the ping 50!! Good article.
bump
it's a Lapua .338 magnum
then you can't shoot national match ammo??? damn
“It is our understanding that commercially available AR15’s and M16’s – although some are stamped 5.56 Rem on the receiver – are manufactured with .223 chambers.”
Knew something like that was coming, was surprised how far down the page I had to read to find it.
Basic rule of precision consumer-market manufacturing: Do whatever’s cheapest or easiest, eh?. How many of our technologically/numerically illiterate customers are gonna discover or understand the difference?
My original Colt AR-15 is marked .223, but I know it will shoot 5.56 NATO rounds easily. I’ve put several thousand through it including ball, SS-109 and tracer.
While some of this is true, the important factor is head space in the barrel and the bolt. An improperly head spaced barrel/bolt for 5.56 is just as dangerous as a .223 with 5.56mm in it.
Bottom line is that any AR owner knows (or should) that they need to spend time measuring their parts if they assemble it themselves, check the head space, and the leade. Most completed guns are already head spaced in the factory and are set for 5.56.
Service parts are an issue that needs to be considered in an AR type rifle. A matched set barrel/bolt is significantly more expensive than either of the parts individually. Not that setting the headspace is that difficlut, and the gauge block is $15 or $20. Obviously, too long can be corrected (shaved to meet the spec), too short is dangerous and hard to determine even with the gauge.
They are one and the same. There is no difference.
The converse problem with putting .308 into a 7.62x51 NATO chamber is too much headspace. It might not fire reliably with the case head not resting properly on the bolt face. Gas may well escape around the shoulder of the brass too.
I reload my own .308 with the 100 gr Speer "Plinker" for punching paper targets. Less recoil, good accuracy and total control of the cartridge dimensions.
If you buy a top of the line Bushmaster or Colt from the factory set up the way you want it in the 5.56 it will be perfectly on the money. If you spend half as much and get a knock off AR you have no idea about headspace or where the parts came from. Bottom line is step up and spend $1,200 - $1,900 for a top grade weapon.
Our M-4 Bushmaster has matchgrade barrel and trigger and is stamped 5.56 on the barrel and the receiver. .223 in this weapon is not very accurate however when we use Lake City or Federal 109’s in 55 grain FMJ or 62 grain tracers we get a 2 inch group at 200 yards. Again this is what you get when you buy from the factory set up the way you want it.
If you want an off the shelf weapon get an Ak.
That’s why I am suspicious of this article’s premise.
Had a FReeper here tell me that he didn’t know anything about a ‘leade’ and .223 vs 5.56mm cautions because he’d never seen anything about it. I sent him a treatise on this very subject as a lesson. Never heard a word back from him.
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