Throwback Thursday: AR-15 .223 vs Mil-Spec 5.56mm Chambers

.223 Rem vs. 5.56mm Nato

When it comes to AR-15 .223 vs Mil-Spec 5.56mm chambers, what are the biggest differences? Most people do not know. They say, “I think you can shoot both kinds of ammo through either one, right?”

Then, they buy an AR-15 and start to get more educated. Frequently, they later have regrets they did not get the AR with a chamber they wanted because they did not know what to ask.

We are going to cover the major options in AR-15 chambers, including Mil-Spec chambers and the benefits of each. I am going to limit this to .223 Rem. and 5.56mm chambers and will address ARs with other calibers, such as .308 (7.62×51 NATO), in the future.

There are three types of chambers in the M16/M4/AR-15/MSR family of rifles, but most people think there are only two.

  • The first is the Mil-Spec 5.56mm chamber, which is used in the M16 and M4.
  • The second is the .223 chamber, the most common chamber in AR-15 rifles, although you can get AR-15s with a 5.56mm chamber. (Why you would want that is very interesting and I go into that in detail below.)
  • The third is a .223 Match chamber, which is used in AR-15s by serious, competitive AR-15 shooters.

.223 Rem Chamber

First, let us cover the most common AR-15 chamber: the .223 Remington chamber, commonly called .223 Rem or just .223. Most AR-15s also come with chrome-lined chambers and barrels.

It does not make sense in the manufacturing process to only have the bore (barrel) or only the chamber chrome lined, so if you read a spec sheet that says an AR has a “chrome-lined barrel,” you safely may assume the chamber is chrome lined as well.

.223 chambers are made to SAAMI (Sporting Arms and Ammunition Manufacturers Institute) specs, not Mil-Spec, so the chambers are slightly tighter and smaller than Mil-Spec 5.56 chambers.

Normally, that is not a problem since the most plentiful ammo available to civilians is .223 and not 5.56mm. But many people buy ARs with .223 chambers because they do not know any better, and then they find out there are drawbacks to ARs with .223 chambers.

Drawback #1: The Myth of Using 5.56 mm Ammo in a .223

The first drawback to .223-chambered ARs is the myth that you can shoot 5.56mm Mil-Spec ammo through it. Manufacturers that print the two calibers on rifles and in rifle manuals synonymously further perpetuate that myth.

varmageddon .223 remington ammo
Nosler Varmageddon ammunition is a premium line of .223 Remington ammunition.

You can shoot 5.56 through your .223 chambered AR-15—but you may regret it.

Since 5.56mm Mil-Spec ammo is loaded hotter, it has higher chamber pressure. Built to SAAMI specs, not Mil-Spec, the .223 chamber is ever so slightly smaller than a 5.56 Mil-Spec chamber. So when you shoot 5.56 in a .223 chamber, the case cannot expand as much as it would in a 5.56 chamber.

Therefore, a couple of things happen with varying frequency. The most common is that you will blow primers; that means you will have the primer blow back into the receiver, which decreases reliability as it rattles around in your receiver or on top of your magazine.

You also will experience an increase in failures to eject the spent cases because the case has expanded so much from the hotter load in the smaller chamber, and you may not get the case out of the chamber without putting a rod down the barrel. Shooting Mil-Spec ammo through a .223 chamber also may crack your upper receiver. This is less common, but still happens, and is potentially dangerous to the shooter and nearby people.

So you can shoot 5.56 through a .223 chamber, but it is highly inadvisable, as both are not equally safe for your AR-15.

Drawback #2: Heavy Bullets

The second big drawback to a .223 chamber is shooting heavier ammo—77 grains and above. This is the preferred bullet weight for national match shooters and snipers. The problem is that those rounds are slightly longer than lighter AR ammo, so the projectile is sticking slightly farther down the barrel when you chamber the round.

The problem becomes very obvious when you try to eject the heavier round from the chamber without firing it. This happens because the heavier projectile is slightly longer. On occasion, the rifling grooves may grab it when you try to eject it. The result is that you pull your charging handle back and the case comes off the bullet, spilling unspent powder on the receiver (and your magazine if you did not remove it first).

As it ejects, you are left with a projectile in the barrel, and you will need a cleaning rod to knock it out. Then you will have a mess, and it is not fun—especially when you are on the firing line at Camp Perry competing for the national championships.

.223 Match Chambers

This brings us to the .223 Match chamber. Most .223 Match chambers are not chrome lined. The biggest difference in .223 Match chambers is that the rifling does not begin as quickly, so you do not have the problems referenced above with the case coming off the projectile if you try to eject a live round from the chamber.

This is the preferred chambering for serious competitive shooters who like to compete at the national level, such as at the NRA National High-Power Long Range matches and CMP (Civilian Marksmanship Program) matches at Camp Perry, Ohio, each summer.

5.56mm Mil-Spec Chambers

Then there are Mil-Spec 5.56mm chambers. These are always chrome lined in the M16/M4s for the military and typically are for their semi-auto AR-15 brothers. The 5.56mm Mil-Spec chamber is slightly larger than a .223 SAAMI spec chamber because the Mil-Spec ammo is loaded hotter and has higher chamber pressures.

Benefit #1: Use Both .223 and 5.56 Ammo

So the supreme benefit of 5.56 chambers is that you can shoot .223 ammo and 5.56 out of a 5.56 chamber without reliability or safety concerns. That gives you the flexibility to take advantage of the great military surplus ammo bargains when they are available.

The downside is that, at greater distances, some shooters think they will see a decrease in accuracy shooting .223 ammo through a 5.56 chamber because the chamber is ever so slightly larger.

I think that is arguable. I know what you are thinking: “How much decrease in accuracy?” and “At what distances does it make a difference?”

I believe that 95% of shooters will not see a measurable difference, except at extreme distances for which they may not have the training to shoot effectively anyway. Remember, when it comes to shooting, most of the time “It’s the Indian, not the arrow.” Remember, I am talking about shooting .223 ammo through a 5.56 chamber only—not 5.56 through a 5.56 chamber.

Benefit #2: The 5.56mm Chamber Has a Slightly Longer Throat

The second benefit of a 5.56mm chamber is that it also has a slightly longer throat/free bore area. In simpler English, that means that there is more space between the projectile and the rifling. Remember when I explained what happens when you try to eject a live round when it is 77 grains or above from a .223 chamber (not a .223 Match chamber)? Well, that does not happen with 5.56mm chambers because of the longer throat.

Benefit #3: Availability of Ammo

The third benefit of having a 5.56mm chamber on your AR involves a little paranoia but isn’t unfounded (although I pray it never happens. Some of my prepper fans out there believe there may be martial law one day in America, which would include an attempted disarming of Americans.

5.56 NATO Ammunition
A box of 5.56 NATO ammunition.

That is what Hitler did, so it is not unimaginable.

In any case, nobody can argue that, in an extended time under martial law, you might only be able to get ammo by stealing it off the back of a Humvee—if you do not get shot trying to do so in the first place. I would want an AR-15 with a 5.56mm chamber so you can shoot military ammo through it without added potential reliability problems. And remember, you will still be able to shoot .223 ammo as well.

There is a way to ream out a .223 chamber and make it 5.56mm. I have heard that it is easy, although I have never done it. You might be able to find the reamer, but if I wanted that, I would have it done by a reputable gunsmith.

What Chamber Should I Buy?

So now you may be thinking, “This is really confusing; just tell me what I should get.” It’s a common question when debating .223 vs Mil-Spec 5.56mm.

If I could only afford one AR, I would get one with a 5.56mm chamber.

I also would not trust the labeling on the spec sheet on the manufacturer’s website or even in the owner’s manual that any AR-15 is 5.56mm or .223/5.56mm. I have tested ARs lately that claim, in writing,  that they are both.223/5.56mm. I’ve seen it on their website spec sheets and in the owner’s manual that came with the AR. When I called the manufacturer and asked if the chamber is 5.56mm or is it .223, the manufacturer tech help person dismissively told me it is both.

I stuck to my guns (forgive the pun) and said, “It can’t be both; either the chamber is SAAMI spec .223 Rem. or the chamber is Mil-Spec 5.56mm; which is it?”

Then, from one USA manufacturer, I received the response, “Well, it’s a .223 chamber, but you can shoot both through it.” Another USA manufacturer told me, “I can’t put you through to a tech person, but you can email me, and I will forward your email.”

I did email that customer-service person who could not answer my question, and I confirmed receipt of my email and that the rep forwarded it to the “appropriate person.” That was more than a week ago. As of the time of this writing, I still have no response. I will not own or recommend any of their ARs for the foreseeable future.

Until next time, I will share with you what Ron Mida, one of my shooting mentors always told me: “Shoot Straight!”

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (272)

  1. I used to argue this with people who repeated rumor & myth. I have never seen an AR chambered for true 223, and I wish there was. Think about it: every AR is 5 56, but nearly all ammo is 223. You get the option of shooting either, but at a cost of wasted potential. I would prefer an AR that uses the full potential of the 223. Mine are now Wylde, but even that is a compromise.

    As for the misleading marketing, I just tell people that ammo marked as both is actually 223. Rifles marked as both are 5.56.

  2. Just purchased S&W MP 15 Sport II 5.56
    The barrel has 223 etched near the muzzle. Can I safely fire 5.56x45mm rounds in this weapon???

  3. So I recently bought my first AR, I wanted a 5.56 chambered rifle but got a Match Target .223 because I got a good deal. Might be a stupid question but can I just replace my bolt carrier with a 5.56 bolt carrier and start shooting 5.56 or are there more changes I would need to make?

    1. NO.! First, the problem is not the bolt. The 5.56 chamber has a longer throat which allows for the longer bullets that are usually loaded in the NATO ammo. Second, the BCG you would end up with won’t be any stronger than the match grade BCG you already have. Third, the BCG you have was specifically fitted to our barreled action to get “target-match grade” accuracy. Replacing it will ruin that matchup without gaining any benefit. Fourth, the only reason to shoot the 5.56 ammo is because you have access to economical qualities of it.

  4. Hey I just bought a Remington ar556 and it says I can spit both so my question is since it’s an ar556 does it shoot 556 or 223s or both

    1. I do not know of a Remington 556. I am guessing you meant Ruger 556. If that is the case, yes it will shoot either .223 Remington or 5.56 NATO. ~Dave Dolbee

  5. “There are no differences between the specifications for 5.56 and .223 Remington brass.”

    I have to question the validity of this statement. Every thing that I’ve read states that NATO 5.56 brass cases are thicker in the case wall, perhaps specifically to withstand the rigors of being fired thru belt fed weapons. NATO 7.62X51 ball cases are also thicker in the case wall.

    Reloaders are specifically cautioned, in publications, to never put the same powder load in a NATO case that they may have worked up in a load for .223 or .308 cases as that would or could result in a catastrophic event.

    1. Interesting comment. It is also contrary to anything else I have heard or been able to find out with my own research. So I have to ask you to prove it. Back up your comment with some supporting documentation, or at least some links to reputable publications that show support to your opinion.

    2. Hitler disarmed the German Jews or any Jew in Germany. I’ve never read anything addressing the disarmament of Aryan Germans. He may also have disarmed Catholics and homosexuals, whom he imprisoned, but I have no knowledge of that. I believe he enacted a death penalty for any Jew found with a firearm.

  6. Here is the actual math between caliber – millimeter and vice versa.
    Calibers are generally described in hundreths and thousanths of an inch (i.e. 30 cal, 50 cal, .223, .265 etc)
    The standard conversion accepted throughout the world is 1 inch = 2.54cm where 2.54cm = 25.4mm because there are 10mm in 1cm.
    (i.e. 30 cal = 30/100 or .30 of an inch further if you multiply this by 25.4 you obtain the result of 7.62)
    Regarding ammunition some of these expressions do get truncated.
    Here is the odd thing about all this: .22 directly converts as 5.588 and .223 as 5.6642. If you work this in reverse 5.56 directly converts to 0.2189 which when rounded is .22 or 22 caliber. To the articles point 0.004 inches or 4 ten thousanths of an inch may be imperceptible to the human eye but where chambers and cup pressures are concerned these differences are great. The chamber is designed to keep the cartridge from expanding and even at 0.004 of an inch it makes a great difference.

  7. My AR has the chamber size stamped on the barrel (5.56 NATO 1:8). I don’t know if all manufacturers do that or just mine. That is confirmation in my mind as to the size.

    1. That makes hell of sense. Pressures lost on the 223 cartridge, means less distance, maybe less spin. Thanks for pointing that out.

  8. Great answer! Most people have NO idea there’s any difference between the two rounds, much less the chambers.

  9. I notice a few people say that they prefer the .223 to the 5.56. My wife and I bought each other the S&W AR15 Sporters for our anniversary several years ago. I like it so much better than the Ruger Mini14 that I had 2 of over the years. Both of the S&W’s are 5.56. I reload for most all my guns, but when I can buy a box of 1000 rounds of Federal surplus 5.56 for $250 that tells me I’ve got the right caliber for my rifle. Add the fact that I can still shoot .223 from it accurately. I’m happy with our choice.

  10. I experienced a punctured primer when I first fired a surplus 5.56 from a bolt action Remington 223. I was not wearing shooting glasses (for the last time), and I thought that I had lost eyesight in my dominant left eye. After I got the soot and gun oil out of my eyes and off my face, I put on my glasses and tried it again, thinking that it was just a fluke from the cheap ammo. It was not, and after three shots and three punctured primers I quit shooting. Moral: shoot 5.56 from a 223 chamber at your own risk, but don’t forget to wear your shooting glasses.

  11. Thanks for the detailed information, I knew the basics of this situation before buying my “budget brand” AR. My rifle was certainly represented as having the .556 bore. The only missing information in your article is the actual dimensions of each bore. Easier than contacting customer service is to simply measure your own gun. If you could tell us the different sizes I could measure my rifle faster than typing this post. ( I’m tool and die maker and have my own pin gage set) let us know the sizes and we can check at the store before buying. Thanks -Dave

  12. You cover, very effectively and thoroughly, the AR15, however know one covers, or mentions, the Ruger Mini14. Can you address this fine rifle as well??

  13. This is all BS, every word of it, if any part of it was real the insurance companies and the personal injury attorneys would be all over this, if there was any chance, even the slightest chance, that someone would be injured by shooting a mil spec 5.56mm round through a gun stamped .223, the gun manufacturer would be shut down and the problem would be fixed, but, you see the problem doesn’t exist. I could compare this to older guns chambered for .30-06, the ammo manufacturers will only build .30-06 rounds to the original pressure specs, so they are not responsible for blowing up older guns and hurting someone, the same is true for .45 long colt, none of these companies want to be sued, IF THERE WAS ANY CHANCE THAT SOMEONE WOULD BE INJURED BY SHOOTING A 5.56 MIL SPEC ROUND IN A GUN CHAMBERED FOR .233, THE GUN MANUFACTURER WOULD IMMEDIATELY CALL BACK ALL OF THOSE GUNS AND MAKE DAMN SURE THE GUN COULD HANDLE THE 5.56 ROUND. THIS HAS NEVER HAPPENED , SO, YOU NOW KNOW THAT ALL OF THIS CLAP TRAP IS STRICTLY BS.

  14. Great information! I own a AR-15 Competition H-Bar, the barrel is stamped CMP 5.56 NATO 1/9 HBAR. I also have a Ruger Mini 14 from the early 80’s marked .223 and a Remington 700 BDL heavy barrel marked .223. Going by the markings I gather that I can safely shoot .223 or 5.56 Mil Spec through the AR but probably should not shoot it in the other two?

    I took about a 20 year absence from any type of hunting or shooting due to a career change. I’m now retired and trying to get back up to speed.

  15. I agree with your article. I only have one criticize. It’s a common myth that the Nazis disarmed the citizens, but it’s not true. The Weimar Republic had much harsher gun control laws than the Nazis. The Nazis just made use of the existing legislation. It’s argued that these gun control laws made it easier for the Nazis to assume control with less resistance, but that’s another topic.

  16. I wonder about this in bolt actions. I’ve considered a bolt action in .223/5.56 for ammo availability and prices. Is it safe to shoot 5.56 in a bolt action chambered in .223?

  17. I have no desire to steal 5.56mm ammo off the back of a military Humvee…I’ll stick with the Remington .223 chamber…the ammo is much easier to obtain….If and when push comes to shove…I’ll steal an AR16 off the back of a military Humvee along with the ammunition it shoots.

  18. The way I understand Wylde chambers is, they are mil-spec, but modified to not lose accuracy when firing .223. My almost “bargain basement” Eagle-15, an Armalite AR-15, has a Wylde chamber. And, guess what, Wikipedia has a good article on Wylde.

    1. Ruger Mini-14 barrel is stamped .223 but is a Wylde chamber so can safely fire 5.56—difference in round dimensions between .223 and 5.56 not trivial and not without consequence when attempting to fire 5.56 from any other .223 marked firearm. Manufacturers cover themselves by cautioning to always use ammo for which firearm is labeled and no other…otherwise all bets are off.

  19. There is another variation on the .223 or 5.56 chamber. It is called the Wylde chamber. The throat is elongated and slightly over-bored to allow use of bullets weighing up to 90 grains, being set at maximum cartridge length without touching the lands. I think the free-bore is slightly enlarged also, just in front of the case mouth, tapering to a tight fit just in front of the ogive of the bullet, which would give pressure relief while keeping the bullet properly aligned with the bore. This modification allows the chamber to be SAAMI spec in tightness while allowing the use of 5.56 ammunition safely.
    I can, however, tell you that there is nothing wrong with the military M16A2 in 5.56 where accuracy is concerned. I am retired Infantry and used to instruct basic and advanced marksmanship. With the right rifle and a good ‘lot’ of ammunition, the A2 and the A3 are capable of sub minute of angle accuracy with 62 grain ball ammunition. I have shot 25 meter targets for zero while conducting training with open sights where the three shot groups all hit the dot in the center of the zero target’s circle and made one ragged hole using open sights, and have used (unauthorized at the time) scoped A2’s to shoot 100 meter groups that were inside an inch. Unless you’re shooting Bench Rest competitions, the accuracy differences due to the (very slight) differences in chamber dimensions between the 223 and 5.56 will be masked by other environmental factors, provided good ammunition is used. Mil-spec ammunition is not match-grade ammunition, so don’t go by how accurate it is in your rifle. Keep in mind that each lot only has to meet military requirements for accuracy, which is nowhere near match accurate. Your mil-spec chambered rifle may be extremely accurate, but your mil-spec ammunition may only be capable of 2 1/2 inches at 100 meters from a test barrel. And foreign ammo for sale as surplus may not have passed even that requirement. For example, I have fired Turkish ammunition in 7,62X51 (.308) that wouldn’t print inside 5″ at 100 yards in one of my rifles.
    If you want a match accurate AR in 5.56, the chambering won’t affect the accuracy of the rifle significantly. The ammunition used will. So will the type of barrel, rifle manufacturer and the trigger mechanism. First, buy the rifle from someone like Fulton Armory, who makes very high quality rifles in AR10, AR15, M1A and M1Garand configurations, with accuracy guarantees. Then either buy premium ammunition or reload for match accuracy. Also, while the short barrel M4 configuration is a specialty rifle, and of little use past 250 meters, so stick with the 20 to 24 inch barrels.

    1. Your comments were spot on.
      However – the original article is as misleading as they always are.
      There is no difference between a .223 & 5.56 cartridge. Honestly – there are over a half a billion reloaded cases sold annually made from brass picked up everywhere from military bases to local shooting ranges – who/what would sort these out for the reloading process safely? The .223 was designed to shoot bullets from the 30 – 50 grain range thus shorter OAL needing a shorter freebore. The 5.56 is the same cartridge but loaded with 55 to 77 grain. 99% of military loads are 55G or 62G (M193 or M855) which were designed with a longer freebore = the 5.56 chamber. The pressures are the same for the same load/grain bullet – SAAMI measures mid case and the military (NATO) measures at the neck. Just as with a hosepipe – there is more pressure at the pinch point so the NATO round measures higher and appears “hotter” to people who are drawn to the bigger is better philosophy.. There have been countless double blind tests with both rounds with chronometers and no one has ever been able to consistently identify which round they were firing. THIS is the differece – SAAMI does not test the same way NATO does so they will not comment on using the 5.56. The danger of the 5.56 is that it will most always have a heavier grain bullet which is longer and when you chamber it in the shorter .223 chamber there is less freebore range (length from tip of bullet to the rifling) and thus could build up to unsafe pressures. This would only happen with 77G+ bullets. If you are shooting M193 or M855 you can shoot all day long with no worries – i have done it with tens of thousands of rounds along with my shooting buddies with chambers labeled with dual compatibility and nobody has ever had any difficulties – blown primers – etc… this is the same rifle range cowboy stuff people love to “educate” the newby’s on. Go with the 223 wylde – shoots all available grain bullets safely and more accurately than the 5.56 at longer ranges.
      BTW – a commercial 223 & 556 cartridge hold the exact same volume water and weigh the same and have the same OAL empty – where would the difference come from?

    1. Every thing that I have read about chamber difference is the “throat lead” is longer and a siight different angel. But nothing about the chamber being actually larger. If you look up “cartridge” dimensions for 5.56mm and .223 Rem., you will find they are the same numbers. All the chamber dimensions I have found are for the .223 Rem.
      Where can we get the actual chamber dimensions for the Mil-spec 5.56mm?

  20. Counting your dedicated match chambers, there are then four chambers in this family. 5.56; .223; .223 match & .223 Wylde.

    My rifles are 5.56 from Daniel Defense and two M4 uppers with 1:8 Wylde barrels–an 18″ & 20″.

    The Wyldes will safely accomodate NATO 5.56 & civilian .223. Above 77 gr you may need to feed single rounds as the OAl may exceed your magazines limitations.

    I’m sure that you are aware of all this, I post it for those that do not.

  21. Great info for the owner/operator of an AR type platform who is unaware of the ammo differences.
    However, at the risk of raising the ire of the Lawsuit Gods, would it be possible for you to actually Name NAMES of the offending platforms? Those who balk at specifying or just down right REFUSE to say because, in fact, THEY DON’T KNOW what they are selling for whatever reason?
    Public “shaming,” if you will, has been shown to be VERY effective at creating behavioral changes in today’s business world and I believe it would be used to good advantage in this instance as well, my Good Sir.
    You’ll be accomplishing several (GOOD) goals.
    One, telling the manufacturer they’ve been “outed” and they NEED to come clean and,
    Two, letting your loyal readers know which manufacturers we might need to avoid like the plague because, for all intents and purposes, they are, very nearly, putting OUR safety in jeopardy by their lack of knowledge or downright bullheadedness and/or ignorance. Even if it is only their Tech Support folks.
    See what I did there? 😉
    Anyway, I would personally appreciate knowing who those Bird Turds are who are so reticent and cavalier about failing to KNOW their business and putting some possibly unwitting customers or innocent bystanders at risk of injury.
    Thank you for your efforts.

  22. Thanks Jerry. I’ve been trying to explain this for years, but as you stated, the manufacturers perpetuate the myth. Now I can just refer them to your article. By the way, 5.56 is all I have outside the Grendel. I have not noticed any significant difference in accuracy up to 200 meters. After that the hotter load of the 5.56 begins to show itself. With much greater penetration. And slightly tighter groups. Again thanks.

  23. That’s why I prefer “Bolts”! I have a “Frankenstein” 98k Mauser, chambered in 8mm-06 with a Japanese Type 38 Barrel “Rebored to accept a .35 Whelen (9.1×63.34mm)…

  24. Thank you for a thorough explanation, it’s so hard to find articles where they actually discuss the topic, so thanks, good info.!

    1. What about the Wylde Chamber. This chamber design is said to be constructed to allow safe firing of either 5.56 mm NATO or .223 Rem. My Springfield AR-15 has such a chamber.

    2. I have the ARmalite 15 and the barrel says 223 Wylde and that is exactly as you described it – shooting either bullets without problems

  25. Picked two Stag Arms AR 15 lowers recently. What is your opinion on 5.56 Stag uppers? Your article explaining the diff btw 5.56. & .223 was very informative. Thanks.
    Army and Law Vet

  26. What is your opinion about Stag Arms uppers? Recently, I purchase two Stag Arms lowers, but waiting to complete both ARs. I been researching uppers for some time, including the Crossroads Gun shows. Your article about 5.56 vs .223 is very informative. Stag advertises 5.56 chambers:
    “Action: Semi-auto direct impingement
    Chamber: 5.56 NATO – this rifle will also shoot .223
    Twist Rate: 1/9 button rifled
    Muzzle Device: A2 flash hider (Stag Arms Compensator on post ban models)
    Barrel: 16″, 4140 steel, chrome lined, government profile, manganese phosphate coated
    Handguard: Free float Diamondhead VRS-T handguard
    Upper Receiver: Forged and mil-spec 7075 T6 aluminum with type 3 hard coat anodizing and a picatinny rail on top
    Bolt Carrier: Standard bolt carrier with a manganese phosphate coating”.
    Army and Law Enforcement Vet

  27. it is my understanding, according to RUGER, their MINI 14 has a WYLDE chamber specifically for all the reasons mentioned. it came in the MINI, before RUGER introduced their AR 556 MODEL.

  28. This is easy. If you buy a 5.56 chambered gun, you can run both the 5.56 and the .223. If you buy a .223 chambered gun, you CANNOT run 5.56 ammo in it. They create a lot more pressure as they are loaded per Mil specs. You’ll end up with split cases, possibly injury to you and damage to your gun. I’ve heard some people say or comment on here you can shoot a 5.56 in a .223 chamber. Simply not true! Period! Now there are some guns that have a Wylde chamber. They are designed to run both safely. So if you want to shoot both calibers, then get a 5.56 gun, or one with a “Wylde” chamber. It’s that simple. Anyone that says you can safely shoot 5.56’s out of a .223 chambered gun, is ignorant and most importantly WRONG. Just Google it and you’ll se I’m 100% correct!

    1. @ Derek – Wow! Great job basically copying everything that was written in the article, and then taking credit for it. Don’t hurt yourself while trying to reach around to pat yourself on the back.

  29. It’s a never ending question for folks new to the AR15. Here’s the straight shot: Forget what it may say in a description about what a particular AR15 will shoot caliber wise. You must look at what’s stamped on the barrel to be sure. If it says 5.56, then you can shoot both the 5.56 NATO AND the .223. If it says only says .223, then that’s all you can shoot. The 5.56 NATO creates higher pressures and requires more headspace. It’s not safe at all to try and shoot a 5.56 in a chamber only marked only .223. You can damage your gun and yourself! Now, if the chamber is labeled 5.56/.223, you can also shoot both rounds safely also and be fine. Typically, these are called “Wylde” chambers and a good barrel to have. A bit less common. Again, If you want a 5.56 make sure it’s stamped on the barrel!! Here’s a link to the “Wylde” chamber at the end just in case you’re interested. Good luck and have fun choosing your new gun! There’s so many to choose from now! A lot of good ones for $1,100-$2,200 range. Don’t believe anybody that says it’s fine to put a 5.56 in a .223 only chamber!! If you have any doubts, go straight to the mfg. and check with them first, email, phone, etc. “Wylde” chamber link: (

    Just paste it into your browser if it doesn’t create a link when I send this to you.

  30. I’m in the market for an AR chambered in true 5.56 MIL spec, and this double label crap has been driving me nuts. ASSHOLES, the lot of them. If the chamber isn’t 5.56mm Mil-Spec then don’t even bother putting 5.56 in the description! So much for integrity. Looking at the Rugar AR-556 at the moment. I miss the days you could pick up a decent SKS for $75. Damn.

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