The length and angle of the barrel leade area defines 5.56 NATO, .223 Wylde, and .223 Remington SAAMI chambers. Predominantly, most aftermarket AR-15 barrels have a 5.56 chamber, also known as NATO. This is the Mil-Spec standard and should not be confused with a .223 Remington or .223 Wylde chamber.
It should be noted that .223 Remington which is technically a SAAMI spec commercial cartridge, and the 5.56 NATO (Mil-Spec) cartridge are patently the same dimensionally. Either cartridge will chamber in either chamber. Internally the cases are also very close dimensionally, and the internal volume can be verified by the old stand by test of using water to measure it. As far as the cartridges go, the difference between the two is pressure level. The 5.56 NATO is radically higher pressure. So, even though the following has made its rounds for years, here it is one more time. Never fire 5.56 NATO spec ammunition in a .223 Remington chamber. There, that clause is out of the way.
When choosing a barrel for an AR the first thing I do is to determine the purpose of the gun. This will drive the rest. With the barrel being one half of the engine of an AR, the rest is built around it and the BCG. For most purposes my routine recommendation is to go with a 5.56 NATO chamber that is properly spec’d from a quality manufacturer. What this provides you with is a barrel that will reliably chamber and safely fire 5.56 NATO and .223 Remington ammunition.
Over the past several years, another option is increasingly available, and increasingly popular, and that is a .223 Wylde chamber. In my experiences with talking to individuals, reading info on the forums, as well as in social media groups, it’s also greatly misunderstood.
Bill Wylde was one of the early pioneers in pushing the boundaries in AR-15 accuracy. When the AR-15 was finally approved for use in NRA High Power Rifle competition, Bill Wylde set out to exploit the accuracy potential of this platform. But there were some hurdles, and one such was that much of that potential could not be realized until there were better .224-caliber bullets available. With the introduction of the 70, 75, and 80-grain VLD designs and shortly after, the Sierra 80-grain MatchKing, that world changed. It wasn’t long until the AR-15 became the Service Rifle winner, toppling the M14 from its former place of prominence.
NRA High Power rules require firing rounds fed from a magazine for the rapid-fire events. For the slow-fire events, including the all-important 600-yard stage, rules say the rounds must be loaded one at a time. With the development of the heavier bullets they had to be seated out a good deal beyond the box magazine limitations of 2.260” OAL.
Remember, the difference in a .223 Remington chamber and a 5.56 NATO chamber is that the NATO has a considerably longer leade with a gentler slope into the rifling, which provides more volume for expanding propellant gases to occupy. This allows for lower pressure results but with a longer bullet jump to the rifling in most cases. But, it is this longer lead that allows the heavier bullets to be loaded longer.
On the flipside, the commercial spec .223 Remington chamber uses a leade that is too short for the optimal seating depth of the longer bullets and cartridge OAL. The .223 Remington chamber is at times referred to a match chamber or SAAMI-minimum. Meaning that these longer bullets had to be seated well back into the case, even when seating depth was adjusted to let the bullet touch the lands at rest in the chamber. The downside to this is that it eats up valuable volume that otherwise could be occupied by propellant.
This is where the .223 Wylde comes into play. Bill Wylde thought that the leade of the 5.56 NATO was too long. The Wylde chamber that he blueprinted is a compromise, not an ideal. His idea was to improve performance with the long bullets by giving more leade and also at the same time to hold jump to a shorter gap with the shorter 69-grain, and later 75- and 77-grain, bullets loaded at magazine OAL’s. If you look at the reamer specs for .223 Remington SAAMI commercial, 5.56 NATO, and .223 Wylde, you’ll see that the .223 Wylde is indeed right in the middle in throat length.
So how does this translate? The way that competitive High Power shooters talk about chambers is based on the overall cartridge length. In the past that would translate to, what would put a Sierra 80-grain MatchKing touching the lands? So to give you an idea, here were some commonly used cartridge OAL’s with that specifically in mind. For the .223 Remington SAAMI it was 2.395”, .223 Wylde 2.475”, NATO 2.550”.
You may have noticed that I have not touched upon the use of the 90 grain VLD bullets. There is a reason for this. In my experiences and in those of others that I’ve known to use them, a custom reamer is required which will lengthen the leade of the barrel to that beyond that of the 5.56 NATO. Therefore, as it relates to the .223 Wylde chamber I do not find it to be applicable to this article.
Let’s talk angles for a moment and how they affect accuracy. What really matters to accuracy for a jumping bullet is the leade angle, and the shallower the better. The .223 Wylde and 5.56 NATO use 1.25 degree and 1.20 degree transition angles, which are very shallow. This is also one way to get the longer leade. Both the .223 Wylde and 5.56 NATO utilize a more gentle transition for the bullet as compared to the SAAMI-spec 3.2-degree leade.
So….. Should you get one? Maybe. Compared with a 5.56 NATO, a .223 Wylde offers a shorter jump to the lands with any bullet. That’s a bonus. But once jump gets over 0.015” or so, there’s not much improvement to be had. The .223 Wylde might be the best overall for the accuracy seeking AR-15 owner because it’s a compromise with no real downside. It safely accepts higher pressure and shoots well. In my experiences of building and testing AR’s that utilize both the 5.56 NATO and the .223 Wylde chamber, I have found the .223 Wylde to provide better precision than the 5.56 NATO barrels with high quality factory ammunition, as well as with handloaded ammunition.
If you’re looking for a 16” or shorter barrel that utilizes a carbine or shorter gas system, I’d stick with 5.56 NATO. Being that most .223 Wylde barrels on the market are made of 416R steel, I also would not utilize one in a role that has a high firing schedule demand. This also applies to an AR-15 that you want to take to the range and do mag dumps with. My personal .223 Wylde chambered gun fill two particular roles. One is a mini-recce role, while the other is more of a cross between the SPR and DMR style.
Overall though, I think the best application of a .223 Wylde is for someone looking to maximize ammunition performance, which combines accuracy with velocity, in a rifle-length setup. And this is especially true for the handloader who wants the option of choosing and using the longer bullets. Understand though, that moving a long bullet out to touch the lands in a 5.56 NATO chamber results in excellent accuracy and still more propellant space. The difference is in magazine-length-round performance, and that’s the edge the .223 Wylde gives us.
If you’re never going to handload to maximize the performance of your gun/ammo combination. If you’re never going to utilize factory match grade ammunition that uses heavier and longer bullets. If you’re not shooting out to distance, and yes, “distance” is relative term. If you’re only looking for minute of man accuracy. If you want to only do mag dumps or make expensive noise by quickly throwing lead downrange and getting the barrel excessively hot. Then the .223 Wylde chamber is probably not for you, and you’d be better served by the 5.56 NATO chamber.