Hi guys, thanks for tuning in to another "Ask Ian" Q&A on ForgottenWeapons.com.
I'm Ian, and our question today comes from Michael on Patreon who says,
"Can you talk about the differences between .223 Remington and 5.56 NATO.
Or in more general terms, about the possibility of using military grade ammo in civilian rifles.
I've heard everything from it will explode, to it will work perfectly."
OK, so we've actually got two questions here, let's start with .223 versus 5.56.
This is definitely something that has a fair bit of uncertainty.
... And I think the uncertainty is fuelled by the fact
that the United States in particular is a very litigious society, and nobody really wants
to go out there and actually say in an official capacity
that it's just fine to use ammunition that is not the type actually specified on the firearm.
... OK, let me do the short version first.
The short version is: it doesn't matter, don't worry about it.
The longer version is: if we look into the history of the 5.56 and the .223 cartridges,
the [AR-10] of course was originally developed for 7.62 NATO.
This was a standardised cartridge at the time,
there was no cartridge development that went into the AR-10.
But when they scale it down to the AR-15,
there is no really suitable appropriate intermediate cartridge for the AR-15 to use.
So ... in early experiments the scaled down AR-15 was chambered for .222 Remington.
However, .222 Remington was a bit underpowered for what
... ArmaLite ... was looking for at the time.
They wanted a little higher velocity, a little higher pressure,
and the .222 case just couldn't quite handle kicking the pressure up to get the desired velocity.
So they redesigned the case, they did a little bit of work on it,
they renamed it the .222 Remington Special,
which in 1959 became the .223 Remington.
This cartridge was submitted to SAAMI,
which is the standards organisation for firearms cartridges.
This is sort of like proofing in Europe, but not really.
Anyway, it's a private organisation that sets all the standards for cartridges.
And those standards are voluntarily adhered to by the firearms industry worldwide, basically.
So in 1962 SAAMI standardises the ... .223 Remington cartridge.
Now the military would go on kind of tweaking some of the dimensions of the chamber
in order to get the best balance of velocity and pressure curve, and all that sort of stuff.
And the NATO standardisation of this cartridge didn't start until 1967,
and it wasn't actually agreed upon until 1977.
So there is a lot of years of time during which this cartridge is tweaked
before the military chamber specification is pretty much set down.
Now something that's important to know about SAAMI cartridge standardisations
is that they generally do not change over time.
Once the cartridge is standardised, it's fixed.
This isn't quite a 100% rule, but it's basically a 100% rule.
The issue is you want to know that a 1911 made in 1911
can still safely shoot the same .45 ACP ammunition that you can buy in 2022.
There are some problems with cartridges that you'll see like .45-70 being a good example,
where originally a black powder cartridge that has now started being loaded with smokeless powder.
A modern production hot-loaded .45-70 is just fine in modern guns, but it will blow up old guns.
The fact that SAAMI specs don't change prevents this from being a much larger problem.
... .45 is a good example.
To my mind, .32 ACP is perhaps one of the best examples of why this is a good idea.
There are a whole slew of .32 ACP pistols that were made all the way back
into the very end of the 19th century.
So like 1899 .32 ACP became a thing.
And you can still shoot those guns with ammunition you can pick up in a store today, 123 years later.
But the downside of this is when you have a cartridge like .223 Remington
that is sort of overtaken by 5.56.
The .223 can't change, it can't be modified to meet the current standard,
because we don't want to risk having older guns made dangerous
by changes to the ammunition standard.
Now in this case the changes to the ammunition standard are really essentially trivial.
The cartridges themselves are interchangeable.
The dimensions ... are going to vary between two cartridges of the same calibre
between two manufacturers, not a lot, but little tiny bits.
.223 and 5.56 are completely interchangeable and will work in either chamber
in basically any rifle outside of very far off the end of the bell curve guns
with either really terrible quality control or
really tight specialised specifications that this question really isn't applicable to anyway.
If you're running some really fancy .223 semi-auto,
but it only takes one cartridge at a time because you've got this
like 100 grain bullet that you're hand loading, this question isn't for you.
This is for people who have like,
"I went and bought a rifle that says .223 on the side of it, is it safe for me to actually shoot 5.56?"
And my answer to that would be I've shot an awful lot of 5.56 in this thing
and never had a hiccup with it. And I think that's generally the case.
Now the differences between the two chambers are slim,
they mostly apply to the shoulder and the neck area.
In particular, ... essentially how tight is the front end of the ... chamber?
Which means how much pressure does it take to push the bullet
out of the neck of the case and into the rifling?
And the more space you have in there, and we're talking thousands, or ten thousandths of an inch,
and we're talking microseconds of difference in the amount of time
that it takes for the bullet to start moving.
Those differences will have a small, but measurable, effect on chamber pressure.
The faster the bullet can move out, the larger a volume you
get in the cartridge case, and the lower your pressure goes.
A little bit extra time taken to push the bullet out of the case, and now
your volume stayed the same, the powder is still burning, the pressure is going to get higher.
There are safety ... specifications, like there's the
accepted maximum limit that your ammo is allowed to produce.
And then there's what is the actual capacity of the rifle?
And in this case I don't think I've ever heard of a situation
where a cartridge going above its stated maximum allowable pressure
has actually exceeded the capacity of the barrel that it was in, causing it to explode.
... If you talk to gun ... shop owners, you'll find a lot of them who have all sorts of stories
about guy comes in looking for 9mm, they don't have any, so he buys 9 Makarov.
The shop tells him, "You can't use that ammo. It's completely different and wrong."
Guy says, "You're idiots, like screw you," and walks out with 9 Makarov.
And then comes back later trying to return it because it doesn't work.
Like, there's a lot of people out there who do not look
closely at any of this stuff and just really don't care.
And if there was an actual problem running 5.56 in a ... .223 chamber,
you would have heard about a bunch of guys with blown up guns by now.
And I've never heard of a single one blown up from this.
So the rule of thumb is if you want to be super careful, you can run .223 in anything,
you should only run 5.56 in 5.56 chambers.
But in the end, I don't think it really makes a big difference.
Worst case, long-term wear on some of your other operating parts
may be a bit worse if you're running hot ammo in a tight chamber, 5.56 in a .223 chamber.
Now the other half of this question was about military grade ammunition.
This is something where I think there is also some misunderstanding,
but it's more among people who have less background knowledge on the subject.
Essentially I would go out on a limb and say military-grade ammunition is the same stuff
that you are buying in civilian packaging, just made to a lower ... priced bid.
... OK, so there are two things. There is like, "I'm buying military surplus ammunition,
so it's military grade. Is it safe to run that in my civilian rifle?"
And the answer to that is absolutely it is, assuming the ... chamber is the same.
Running military 7.62 NATO in your civilian M1A,
or civilian FAL, or G3 or whatever, yeah, absolutely totally fine.
What you'll probably find is that your military surplus ammo is
not quite as precise and as accurate as your civilian packaged ammo.
Now there is a place where military ammo has a substantial difference,
and that is in specialty loadings that have different components inside the bullet.
So there is armour-piercing ammunition, there's tracer ammunition.
That stuff is all perfectly safe to fire in any rifle of that calibre,
but it may have unintended effects on the target.
So for example, you do not want to shoot military armour-piercing ammunition
at steel targets because you'll make holes in them or dimple them.
And you'll damage the targets and whoever owns those targets will be very unhappy with you.
You do not want to shoot military-grade tracer ammunition in dry places in the summer,
because you can, and people every year do, light the range on fire.
And that's embarrassing and not a good thing.
But ... like there's this notion out there I think that military ammunition is the "good" stuff,
and the civilian ammunition is somehow de-rated to be less good.
And there is simply no truth to that matter, ... it isn't, it's the same ammo.
In some cases the military accuracy specifications are a bit less.
Or the military ammo is being sold because it maybe didn't meet all of those specifications.
So really I think the answer here is it's kind of the opposite
of what a lot of people would actually anticipate.
Anyway, I thought that was a good question (a good pair of questions actually) to take on.
That's something that I do get asked a reasonable amount, so thank you for the question Michael.
If you would like to have one of your questions answered
in a video format like this, head on over to either Patreon or Utreon.
I put up requests pretty much every month
on both of those platforms to get questions for videos like this.
Thanks for watching.