When it comes to one of the most common and most produced calibers ever made, the number of choices can be really overwhelming!
A little bit of knowledge can go a very long way and picking the best ammo for your needs isn’t as hard as it might seem.
From twist rate to steel Vs. brass to what exactly “XM” and “M” really mean, we got that and the 6 best 5.56 ammo for your AR coming right up!
.223 Remington Vs. 5.56 NATO Vs. .223 Wylde
The short version is that any barrel marked 5.56 NATO or .223 Wylde can safely shoot BOTH .223 Rem and 5.56 NATO.
Barrels marked as .223 Remington should ONLY be fed .223 Remington. Technically, these are chambers – not calibers. The differences are minor but basically, .223 Rem is a slightly smaller chamber.
This is great for accuracy and consistency, but not great if you’re military mass-producing ammo by the billions. When 5.56 NATO was adopted, it was adopted with slightly higher max pressures than .223 Remington.
To offset that, the chamber is cut slightly larger.
Wylde is a mix of the two. Not as small as .223 rem, not as large as 5.56 NATO. This gives you the ability to use both ammo types but also squeeze out some extra accuracy.
.223 Remington barrels are very rare in AR-15s these days, but there are some very rare exceptions out there.
Table of Contents
Matching Twist Rate To Bullet Type
Twist rate is the speed that your barrel imparts a twist on the bullet. Just like a football through the air with the perfect spiral, adding a twist to the bullet makes it fly with a lot more stability.
For barrels, this is expressed as 1 twist per inches. So a 1:12 means the bullet twists a full revolition, every 12 inches of barrel. A 1:8 would be 1 twist per 8 inches.
Don’t worry if your barrel is shorter than your twist, you don’t actually need to fully twist the bullet to get the right spin.
In fact, oddly enough a bullet will be spun enough with as little as 1″ of barrel. Weird, right?
Choosing Your Twist
Technically speaking, how much twist a bullet needs to be in the sweet spot depends on how long the bullet is.
However, length is annoying for people to pay attention to and since weight very closely correlates to how long a bullet will be – we generally use the weight of the bullet to match the twist.
For any normal application, this is totally fine.
Popular super common weights for the AR-15 in 5.56 NATO range from 55gr to 77gr.
Anything lower is really only used for varmint hunting and anything higher is heavy for caliber long-range precision rounds.
If you want a do-all barrel I highly recommend a 1:8 twist. 55gr will do well in it and the heavier 62gr and 77gr will do amazing.
For a varmint hunting barrel, the classic 1:12 is beastly.
1:7 was the gold standard for do-all rifles and is the standard for M4 rifles, but this is mostly due to the need to stabilize tracer rounds that are longer than normal.
The 1:8 twist is much better for anyone not constrained to what the military does.
XM Vs. Milspec
You’ll run into a few types of ammo like XM855 or XM193 and you might be wondering what makes them different than the official military M855 and M193 (or any of the other XMs and Ms).
Basically, nothing. It’s meaningless. Technically speaking, this isn’t regulated terminology. Some manufacturers call their ammo “XM” and some call it “M”.
The brands that use “XM” say they use it to differentiate from their “M” SKUs that are tested and sold to military or LEO customers.Â
“M” doesnât mean you’re actually getting proper 100% real live mil-spec ammo unless that brand also has military supply contracts. “M” doesn’t mean you’re actually getting proper 100% real live mil-spec ammo unless that brand also has military supply contracts.
Green Tip M855 5.56 NATO
Another major ammo type you’ll run into is the “Green Tip” 5.56 NATO. M855 is the official military name for a 62-grain steel core 5.56 NATO cartridge.
There are a few pros and cons to Green Tip ammo, personally, I say there are more cons than pros.
Technically, M855 isn’t “armor piercing” due to the way the ATF defines AP rounds â so itâs totally legal for civilians to buy.
However, it does have increased penetration.
But it is also more expensive than other types of ammo, it is often not as accurate, and the penetration is far more effective on barriers than it is on armor.
Granted, M855 will fly right through most level III armor and all soft body armor. But that’s basically why level III+ armor was designed, to beef up the level III so it could stop M855.
If a bad guy is wearing armor, I would be surprised if they’re wearing level III when III+ is widely available and basically the same price.
That said, M855 is great for punching through barriers.
While a huge stockpile of M855 for the end of the world might be nice, it’s not the most practical round for anything else.
Steel Vs. Brass Case
In times like these, a lot of us are turning to whatever the cheapest option is. Generally, that is going to be steel-cased ammo.
Steel is a totally viable case material, 7.62×39 has been using it since it was designed. But it isn’t as nice as brass casing.
Brass is softer and will expand in the chamber better for a tighter gas seal while also being easier to extract.
Steel doesn’t expand as well or extract as well, this makes it dirtier to run and requires more gas pressure to extract it.
With being super cheap the best thing about steel cased ammo, it is more forgiving as to what is within spec. An extreme spread of 50-70 feet per second is more likely than not.
Malfunctions are more common with steel case ammo, but not horribly so. Lucky Gunner tested 10,000 rounds of two kinds of steel cased ammo (20k rounds total) and 10k rounds of brass cased.
Their findings resulted in zero malfunctions for the brass, but a combined 24 malfs for the steel cased.
Roughly 1 malfunction per 1,000 rounds for steel-cased ammo really isn’t bad, as long as your life doesn’t depend on it.
Steel is also harder on your rifle. While steel case is normally coated in a lacquer to aid in extraction, it will still wear down your barrel’s chamber and throat more quickly than brass will.
It will also tend to break extractors more often.
Extractors are cheap to replace, but a new barrel adds up. Generally speaking, running nothing but steel an AR-15 barrel will last 8,000-11,000 rounds before you run into major reliability issues and major accuracy issues.
Running nothing but brass, you can get around 15,000 rounds of barrel life.
Show Me The Money
But the thing is… steel is so much cheaper than even with replacing barrels more often, you’ll still save money in the long run. Sometimes, a lot of money.
As I write this, steel cased ammo is about 32 cents at the cheapest and brass is 46.5 cents.
Assuming a barrel is $200 each and you need a new one every 8,000 rounds for steel and every 15,000 for brass, your total cost for 30,000 rounds of barrel life and bullets fired is $10,350 for steel and $14,150 for brass.
Saving almost $4,000 over the course of 30,000 rounds is a huge amount of money. That’s literally new KAC SR-15 and an EOTech + magnifier money.
Personally, when it comes to plinking and training all I run is steel.
For home defense, hunting, and long range competition I bite the bullet so to speak, and get brass.
Now let’s discuss the best 5.56 ammo!
6 Best 5.56 Ammo for Your AR-15
Wolf Steel Cased
Back in the good times, this was my absolute go-to recommendation for cheap plinking ammo that will always shoot great.
It still is, but the price has gone up… like it has for everything else.
These days, it’s not so much as “cheap” than it is “not as expensive as everything else”.
Still, it works, it’s “cheap”, and you can find it in bulk and that on its own is a reason to go for it.
I’ve shot thousands of rounds and I have thousands more sitting on my ammo shelves.Â
Speer Gold Dot 55gr
This is one of the gold standards for defensive ammo. Speer Gold Dot is trusted in every caliber they make it in and I would personally bet my life on it.
I like their 55gr version the most because it has less overpenetration in drywall.
When it comes to defending your home against whatever goes bump in the night, this is a choice that might save your life.
Black Hill
Honestly, literally, anything from Black Hills is outstanding ammo. Everything they make is match grade and everything they make is a work of art.
It’s not cheap, it’s hard to find, and when you find it the odds of being able to get more than a few hundred rounds are slim, but man oh man this is great ammo.
My favorite is the 77gr OTM. I’ve shot it from my precision 20″ AR out to 900 yards and it rings steel all day long.
This stuff is too rare and too expensive for everyday use, but if you want to really stretch your rifle out – grab yourself a few boxes and see what you can really do.
Federal American Eagle XM193
55gr brass cased ammo made to a high quality standard. When I want to stock brass ammo deep, this is normally what I pick.
It’s a good price, it’s great ammo, and it never fails to go bang for me.
There might not be anything special or overly amazing about it, other than the reliability, but it’s a tool that does a job and does it perfectly.
Federal American Eagle XM855
If you want to stock up on Green Tip, this is what I love.
Sometimes you can find it already on stripper clips and while that costs a little bit more, I love the convenience of it.
I don’t shoot XM855/M855 very often, but I do normally keep a few mags of it loaded in a chest carrier in the closet next to my go-bag. Because you never know when zombies will wear body armor, right?
Hornady Frontier 55gr
I’m mentioning this one for two reasons, one to dispel some internet lore and two because I honestly think this is solid ammo.
When Hornady Frontier first released it almost instantly got a really bad reputation. And it deserved it. In the first few runs, there were some very bad batches that resulted in some rifles that went kaboom.
No one was hurt, as far as I know, but that is still totally unacceptable from your ammo and doubly so from ammo that comes from such a well-respected manufacturer.
That said, the issue was quickly resolved, a recall issued, and everything since then has 100% good to go.
But because of how bad a rep Frontier got in those early days, you can often find it for a decent amount cheaper than comparable ammo. And hey, cheap ammo is cheap.
Currently, this is great ammo and I would trust it. Just don’t buy any second-hand boxes… just in case.
Wrapping Up
I hope this helps you not only choose the right ammo for your needs but also educate you on some lesser-known topics.
This was a lot of information to take on but it isnât as bad as it sounds.
For cheap shooting, Wolf Steel Cased is awesome.
I trust Speer Gold Dot as my #1 pick to defend my home with, it’s my best 5.56 ammo. But when it comes time for some penetration, American Eagle XM855 is good to go. If you find it on stripper clips, get double!
