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I’ve met Ed Logg before, the programmer/creator behind the arcade classics Gauntlet and Gauntlet II and attended his GDC talk in 2012. (I was the one that asked him the question about those that could play forever at 42:53)

Logg was inspired by this Atari 8-bit game called Dandy, developed by John Howard Palevich as his undergrad thesis project at MIT. Some have suggested the ‘inspired by’ was a lot closer to ‘directly copied’, but it was resolved without lawsuit – Palevich got a free Gauntlet arcade system and is now listed with ‘special thanks’ in the credits.

Check out some of the gameplay from Dandy (below) and see how many similarities you see (4 play co-op, monster movement, etc)

For a little extra fun, check out Ed Logg’s first, unreleased, Atari game – called ‘Maze Runners’ and to see how he developed

When I was first learning about AR 5.56 chambered rifles, there was a lot of confusion about what ammo to buy. This is the guide I wish I had.

First off, if you are training or bought a rifle – GO READ THE MANUAL FOR THE RIFLE. Hopefully you did research on what you were buying before you went to the store. Now you need to go read the manual for your rifle. If you lost the manual, go to the rifle manufacturer’s website and download it.

Now it’s time for practice and training. Just like a learning to drive a car, you should find a good instructor and a safe place to practice. I took a shooting course from my local law enforcement shooting center. It’s a really good idea to learn from experts from the start. They’ll instill safe handling practices and correct mistakes before they can become bad, or deadly, habits.

Many training programs ask you to provide your own ammunition even if they are providing the rifle. So imagine my surprise when I found LOTS of confusion about what to buy for 5.56 chambered AR rifles. Let’s go through them one at a time.

Topics this article covers:

1. 5.56 ammunition naming conventions
2. XM193, XM193A, M855, M193 and other letter designations
3. Full metal jacket, 855 penetrator, frangible, boat tail, and other rounds
4. Weight and grains: 40, 55, 62, 77, and 80 grain rounds
5. 5.56 vs Remington .223
6. Bonus Topic: Other exotic rounds

Topic 1: 5.56 Ammunition Naming Conventions

When I first started trying to buy ammo for my weapon, I ran into hordes of different naming conventions. Here’s some of the ones I saw:

• 5.56
• 5.56×45
• 5.56 M193
• .223 5.56 55 grain FMJ
• 5.56 NATO
• 5.56 x 45mm NATO
• 5.56mm x 45mm 62 grain
• 5.56mm green tip
• 5.56X Full metal jacket boat tail

And many, many other variations. I was lost. Was there any differences? Which was safe in my weapon? What about the designations XM193 or M855 or M193?

The key here is to know that the STANDARD round for a 5.56 AR platform rifle is:

Full metal jacket (FMJ) XM193 5.56x45mm 55 gr (grain) round

If the name is missing a part (like it doesn’t say FMJ, or omits the x45mm or omits the mm like x45) then you can almost always safely assume the missing part matches what is stated above: FMJ 5.56 x 45mm 55 gr. If the round just says ‘5.56’ then you can usually assume it’s a 5.56 x45mm 55gr round.

If there are OTHER things specified, like ‘green tip’, ‘boat tail’, ‘NATO’, or a different number other than 193, that does mean a difference. Just about all 5.56 designated rounds should safely fire from your rifle, but those different characteristics and qualities make their behavior, cost, and use different than a standard 5.56 x 45mm 55gr round. So lets learn some of those differences.

NATO STAMP: Having a NATO stamp indicates a real difference in how the round was made. The NATO stamp is an indication that the NATO spec has been followed when making the round. An official 5.56 NATO round will have a little cross in a circle stamped on it:

You might run into rounds without the NATO stamp but say 5.56 such as these rounds from Prvi Partizan:

Having a NATO stamp has to do with how primers are seated and other technical facts about how the round is made – but NATO and non-NATO rounds should work in your 5.56 chambered rifle. Personally, I only stick with the 5.56x45mm NATO rounds. For me, consistency of quality in the round is more important than saving a few dollars. Rounds without the NATO stamp might indicate lower quality standards and have lower tolerances – so use your discretion.

Topic 2: XM193, XM193A, M855, M193 and other letter designations

Rounds often come with markings on the box about being XM193, M855, M193, and a whole host of other similar lettering and numbers.

In the case of products labeled xx193xx, the various lettering before the number (XM, XP in red) are branding and packaging differences (except one case I’ll talk about below).

The middle number (ex: 193) indicates the purpose and composition of the round. Here, with the middle number, different numbers do make a difference in performance characteristics – though they should all fire just fine from your rifle. The most common and usual round for a 5.56 rifle is a 193 soft homogenous core round.

If the middle number is 855, those rounds are sometimes called 5.56x45mm 62 grain, green tip, penetrator rounds, etc. These are specialized rounds that have a steel core. This leads to different performance characteristics and are not always good for target shooting. See the discussions on composition below for pictures. Information about tracer, blank, and other round designations and types is in the bonus section at the bottom of this article. You can also read more here.

The letters after the number (like C, A, AF, ML, B, etc in green) also almost always have to do with vendor specific packaging differences. The rounds themselves are almost always identical. It is worth making sure you understand the packaging though. Some packaging is more expensive because they come with ammo already loaded on stripper clips. Other letters sometimes designate the ammo is in bulk/loose packaging which might lead to more denting of casings (if that is important to you). Read some examples here.

One exception for 193 rounds is the designation M193 with no other letters. The M by itself in front of 193 indicates these are military grade/spec rounds. These should NOT be available to a civilian customer as selling them in the commercial market is illegal. However, some places claim they are M193 – though this is almost certainly regular XM193 rounds as the M variants should not be available to civilians.

For almost all practical purposes, XM193 is what you want.

Topic 3: Full metal jacket, hollow point, and other rounds

Now we get into bullet composition. What is that little bit of metal that flies out of my barrel made of and why does it matter? Again, you’re going to run into massive amounts of self-styled ‘experts’ talking about all kinds of exotic rounds and why you should be using them. Lets stick with the basics.

Full metal jacket or Ball ammunition: Sounds scary and imposing – but it’s really the most common and standard kind of round. A full metal jacket round (FMJ) is just that – a bullet made of a soft core (often lead) encased in an outer shell (“jacket”) of harder metal. In military nomenclature, the full metal jacket round is often labeled ball ammunition. 5.56 often has a uniform lead core with a copper/copper-nickel jacket or shell. A bullet that has a jacket generally allows for higher muzzle velocities than bare lead without depositing significant amounts of metal or damaging the bores from steel or armor-piercing core materials.

Summary: the full metal jacket rounds is your bread and butter ammunition for your 5.56 rifle. They’re designed to shoot it above all other types. This is almost certainly what you should buy for the range or practice as you learn. It’s often the cheapest and easiest to buy in bulk.

Hollow point and Jacketed Hollow Point:

What about the geometry of the bullet itself? Turns out, there’s also different tip styles. Instead of more penetration, you might want LESS penetration in some cases.

Above are full metal jacket/penetrator rounds have a copper jacket that completely covers the round. They tend to have high accuracy and hit targets while maintaining their velocity. While this is great for range and target shooting because it offers a consistent performance when training – in real situations it often means the bullet exits the back of the target at high speed and continuing on to hit further targets.

Hollow point and soft point rounds are designed to stop inside their target. It does this by expending their energy into the target. It does this by opening up like a mushroom as soon as it hits a target. It’s much like a fist. A fist is easy to push through water, but open your hand and it gets much harder. The energy gets expended into the target instead of just traveling through it. This is a desirable trait if you are using the rounds for personal defense and hunting.

Hollow point rounds get their name from the fact they have a tip that has a hollow space. This means when the hits a target, it immediately expands like opening an umbrella the wrong way in a wind storm. These rounds become highly specialized for their purpose and often sell in small quantity boxes for home defense.

One big problem with these rounds is that they need sufficient time when they hit to expand. When tested, many hollow point rounds don’t actually expand as expected. Pistol rounds are most often associated with hollow point bullets but testers on YouTube regularly reveal many brands do a very poor job expanding when they hit their target – even with slower pistol muzzle velocities. Sometimes they expand only partially, sometimes not at all. This is especially true with 5.56 rounds that have much higher velocities. So do your research carefully if you’re looking into 5.56 hollow point rounds.

Soft Point:

Soft point rounds are as the name suggests. They are mostly covered by a metal jacket, but the tip is not covered and exposes the soft lead core. The soft tip expands on hitting the target, but not as much as hollow points. These are good for large game that have tough, thicker outer hides.

Will these rounds work in your 5.56? Yes – without issue. Just pay attention to their weight in grains and recommendations. Also be ready to pay more and only buy in small quantities. These rounds become highly specialized for their purpose and often sell in smaller quantity boxes. They also might have different accuracy characteristics.

Boat tail:

Above is a picture of two bullets. The left bullet has a standard flat base. The bullet on the right is called a boat tail. The difference is how the bottom of the round is shaped. The standard flat base bullet has a steady straight contour to the tail. A boat tail starts to taper – well – like the hull of a boat. Boat tail bullets were developed to get more range and have less adverse effects when the bullet fell to sub-sonic speeds. Most experiments show no gains using a boat tail over a standard flat base round under 600 yards. All things being equal, a boat tail projectile also has a greater sensitivity to weapon factors not being perfect, either in the barrel or at the muzzle. There’s a decent writeup here and discussion here. Which should you get? Unless you’re doing longer range shooting with 5.56 (not a common thing), a standard non-boat tail round is what you want.

Summary: If you’re going to the range to practice, it is probably best to stick with a standard full metal jacket bullet since they are cheapest and you likely don’t need the specialized features of hollow/soft points or boat tails.
Read more here.

Topic 4: Weight and grains: 40, 55, 62, 77, and 80 grain rounds

Next up, there is also the weight of the round. What’s the difference between 5.56x45mm 55 grain, 40 grain, 77 grain, and other grain amounts? And what about those 62 grain penetrator/green-tip rounds?

People argue endlessly about this topic. Some argue heavier rounds have more ‘stopping power’; others argue about overpenetration, accuracy at distance, etc. The most important part is to get the right one for your weapon and shooting goal because different weight bullets have different performance characteristics.

First, an anatomy and terminology lesson. The term ’round’ or ‘cartridge’ refers to the entire package: its casing, powder/propellant, rim, primer, and bullet. Ammunition is the plural of round/cartridge. A ‘bullet’ only refers to the solid projectile (tip) propelled from the end of the cartridge when the gun is fired:

The weight of the bullet part is measured in a unit of mass called grains (abbreviated “gr.”). One pound is equal to 7000 grains, and there are 437.5 grains in an ounce. This is the metal projectile part of the bullet that leaves the barrel while the casing pops out and onto the ground.

5.56 rounds usually are in the 40-80 grain range. 9mm handgun rounds are in the 115-140 grain range. A 50mm BMG round is a monstrous 750 grains. The most common 5.56x45mm round is 55gr. A 40gr bullet weighs less, a 70 gr bullet weighs more. So why are there heavier or lighter ones – and should I pick one?

You read your rifle’s manual as first indicated right? 🙂 Did it mention anything about preferred round weight? Most 5.56 rifles will indicate a 55 gr round. Or perhaps you noticed a barrel twist amount? Most 5.56 rifle barrels will have a 1:9 twist rate. I’m going to do a mediocre job summarizing this topic – so go read more later – but this should get you going.

One of the great accuracy improvements in early firearm design was the creation of groves inside the barrel where the bullet travels. As the bullet travels down the rifle, the groves start the bullet spinning – and this rotational spin creates stability in flight – which translates into accuracy at distance. There have been whole fields of study done on barrel length and twist rates along with how projectile size, shape, weight, and length affects accuracy, power transfer, and various other performance characteristics. It’s a fascinating topic with lots of great science – definitely worth reading up on.

Science aside, your rifle’s barrel length and twist rate makes certain rounds give the best performance. While you might hear that the bullet weight dictates the twist rate (or vice versa), this is not entirely true – but usually true enough for practical purposes. From a scientific point of view, length of the bullet has more to do with the best twist rate than weight alone. The weight measurement usually still works in our case because heavier bullets are often simply made to be slightly longer in length to achieve the extra weight. So weight is a pretty good practical measure in most cases. Another common mistake is saying that the weight in grains has to do with the amount of powder in the round. The reality is via testing – it has been shown time and again a heavier grain round might have more powder or it just as equally might not. This is a good reminder to be cautious and read solid research papers when reading about topics like twist rates, weights, accuracy, and other performance characteristics because many online ‘experts’ dangerously over-simplify.

At any rate, a simplified chart for optimal 5.56 twist rates to round weight looks something like this:

So what happens if I mismatch the weight and twist rate? It won’t damage your rifle, misfire, or jam. Instead, all that happens is your accuracy usually goes down. This is why M855/62 grain green tip/penetrator rounds are often less accurate than standard 55-grain rounds in most 5.56 rifles – since most rifles have a 1:9 twist rate.

For most AR platforms with standard twist rate barrels, a 55 grain bullet is what you want. Consult your manual. The best advice says to start with what is recommended for your rifle until you are proficient enough to know what you’re doing to choose otherwise.

Topic 5: 5.56 vs Remington .223:

In purchasing ammunition, you may be told/see people selling .223 ammunition for your 5.56 weapon. You’ll see forums where people will tell you one works in the other, others say you cannot. Adding to the problem is that Remington .223 (also called 223 Rem or just 223) and 5.56 rounds will usually fit in either rifle. Some people will swear by and even fire 5.56 rounds in a weapon chambered for .223 Rem and vice versa. So what’s the difference?

The answer is this: 5.56 ammunition and rifle chambers are not the same dimensions and pressure ratings as Remington .223 ammunition and rifle chambers. You can safely shoot .223 Rem in a 5.56 rifle, but you should not fire 5.56 ammo in a .223 Remington rifle.

5.56 rounds can generate higher chamber pressures than Rem .223 rounds. 5.56 weapon chambers are designed to withstand the higher pressures of 5.56 rounds. Rem .223 weapons have chambers that are NOT designed for the higher pressures of 5.56 rounds. Further, Rem .223 chambers and 5.56 chambers do have slightly different internal dimensions. The differences are small enough, however, that either round will usually fit and fire in either weapon.
Reloaded rounds may be another issue to consider. Reloaded rounds often deviate even more from their specs and can result in higher rates of jamming or feed issues. Mixing reloaded rounds with the chamber different dimensions may be even more unreliable.

The actual technical differences between the rounds is quite fascinating if you’re interested. It is especially important if you’re interest in reloading your own rounds. Go read tons of more technical details here or see this video here.

Always check the stamps on the end of the round and make sure you’re putting the right ammo in the right weapon.

Bonus Topic: Other exotic rounds

Here’s some more exotic rounds, as well as a discussion much like we had above.

SS109/M885

Also known as a green tip or penetrator round. This is a 62 grain round with a lead alloy and steel core.

L110/M856 (Extended Tracer)

Contrary to common belief, the M856 does not have a steel core penetrator like the M855. The M856 is merely an extended tracer round with a 63-grain bullet.

M193 (military round)

This is a standard 5.56x54mm caliber 56 grain round, but designated/sold for military use only.

M196 (Tracer)

The M196 usually has an orange or red tip, denoting that it is a tracer round. Tracer rounds burn a chemical compound (usually found in fireworks) that’s glued to the back end of the bullet itself, creating a bright trail in its wake. Most magazines load a tracer every 3 to 4 rounds.

M197 (Test Round)

High-pressure Testing cartridge used when proofing weapons during manufacture, test, or repair. Comes in either stannic-stained or nickel-plated case.

M199 (Dummy)

The M199 dummy round is an insert, used for dry-fire training. Usually used for loading and unloading drills during basic training. Dummy rounds have six indents on the sides of the shell casing to denote that it is a dummy round with no powder inside. The primer is removed so the firing pin can pass through safely with each dry-fire.

M200 (Blank)

The M200 is a functional shell casing with gunpowder loaded inside. At the business end, the casing is crimped with no bullet in place. The crimping allows appropriate pressure to build in the chamber and barrel in absence of a live round, allowing the rifle or pistol to cycle as if it were firing a live round.

M862 SRTA (Short-Range Trainer)

The M862 short-range training ammo, or SRTA, allows for live-fire indoors where rifle ammunition would not normally be allowed. This ammo can be used to train at distances of 25 meters or less. Importantly, many AR-15 owners and military service members zero their rifles for 100 meters, at 25 meters. You should not use SRTA ammo to do this, even though the firing distance is the same. Ballistics for the M862 round are wildly different compared to M855 and M193, and doing this will result in an inaccurate zero.

M855, Penetrator, or Green Tip Rounds:

You might see ‘green tip’, penetrator, M855, or 62gr 5.56x45mm rounds. What about them?

These rounds differ from the standard ball or full metal jacket rounds in that they often have a hybrid core designed to penetrate targets better. A full metal jacket core is usually uniform material inside the metal jacket. But as you can see below, penetrator rounds are often a mix of traditional soft material and a steel perpetrator part.

Will these fire safely in your 5.56 and can I use them every day? Yes. However, depending on your barrel length, twist rate, and other factors – these often turn out to be not as accurate or consistent as full metal jacket rounds on many stock rifles that have 1:9 twist rate barrels. A 1:9 twist rate barrel is best suited for 55gr ammo and may be slightly less accurate shooting 62gr rounds. There’s also some evidence that hybrid core rounds can never be as balanced as bullets with uniform cores – which results in less accurate flight. Here’s some further info and we’ll talk more on that in Paul Harrell’s video at the end.

M995 (Black Tip)

M995 is a 5.56-mm Armor Piercing (AP) cartridge that provides an AP capability for the M16A2 rifle, the M4 carbine, and the Squad Automatic Weapon (SAW). The picture at the top incorrectly labels it as 955 – it should be 995.

Loads more round types can be found here.

Putting it all together:

Paul Harrell has a good YouTube channel on firearm training. One of the things I like about him is that he’s got a tremendous amount of military/police training, is an award winning marksman, certified military instructor, and has years of knowledge. Sadly, he passed away from a very brief fight with pancreatic cancer in Sept 2024.

What makes his videos good are that he backs up what he says with actual, very practical, demonstrations. In this video below, he does a comparison of the standard 5.56 NATO XM193 55gr round and a M855 62gr perpetrator round.

You should now be able to combine everything we’ve learned and understand what he’s talking about and learn a little about how to listen critically to many online ‘experts’.

Links:

Do NOT consider these definitive or completely accurate. I used them for reference of various bits and pictures I needed.

• Bullet types
  • https://www.pewpewtactical.com/federal-m-vs-xm-556-xm193-vs-xm855/
  • https://en.wikipedia.org/wiki/Full_metal_jacket_bullet
  • https://www.ammunitiontogo.com/lodge/what-are-soft-point-bullets/
  • https://www.ammunitiontogo.com/lodge/jacketed-hollow-point-bullets/
  • https://www.calguns.net/calgunforum/showthread.php?t=240167
• Twist rates and grain
  • https://www.pewpewtactical.com/federal-m-vs-xm-556-xm193-vs-xm855/
  • https://americanshootingjournal.com/barrel-twist-rate-affect-accuracy/
  • https://www.luckygunner.com/lounge/choosing-right-bullet-weight
  • https://www.nrablog.com/articles/2017/3/how-to-pick-the-right-round-for-your-ar15-barrel/
  • https://www.ammunitiontogo.com/lodge/bullet-grain/
• 223 vs 5.56
  • Summary of Rem .223 vs 5.56: https://www.americanrifleman.org/articles/2013/3/4/223-remington-vs-556-whats-in-a-name/
  • Tons of technical details on differences between 5.56 and .223 https://blog.westernpowders.com/2019/04/223-remington-and-the-5-56x45mm-military-nato-cartridge-and-chambers/