[ Ask Ian: Man-Portable Chain Guns? ]
Hi guys, thanks for tuning in to another "Ask Ian" Q&A on Forgotten Weapons.
I'm Ian McCollum, and our question today comes from Nikolas on Patreon, Nikolas asks,
"Have there been any attempts to make miniaturised man-portable chain guns?
Do you think there is a future for such a machine gun given modern advances in energy storage?"
So, cool question, this is something we're going to have to tackle in a couple of different stages.
So first off, what is a chain gun?
Secondly, what does a chain gun allow you to do that other types of guns don't?
And then thirdly, is this something that's likely to see further development?
So first off, what is a chain gun?
A chain gun is a specific type of externally powered machine gun.
Of course one of the fundamental advances in firearms technology,
the thing that made Hiram Maxim such an important figure,
was discovering how to ... practically harness the power of a cartridge
to both propel the bullet and also cycle the action of a gun.
Thus allowing you to create a fully automatic ... self-powered gun.
It's a really cool system from an engineering perspective
that essentially your projectile is also your,
for lack of a better term, your battery for making the gun function.
Now there are a couple of different types of externally powered guns out there.
Chain guns are one of them, various types of rotary-barrel things like Miniguns are another.
With a chain gun specifically you actually have a physical chain
that runs in essentially a square around the action.
And it uses the external motor (... always an electric motor),
to perform all the major functions that would be done by a gas operation system
or a recoil operation system on a typical firearm.
So it opens the bolt, it feeds a cartridge in, it closes the bolt.
And then it holds the bolt locked or ... engages a locking mechanism while the gun fires.
And this rotating chain, by altering the lengths of the different sides of the geometric path
that the chain is following you can do things like alter the rate of fire.
You can alter how long the bolt remains locked after the gun fires.
And ... that's important for a reason that we'll get to in a moment.
And it's a nice system, it is ... almost always a single-barrelled system.
And that makes it a little bit distinct from the Minigun type systems
where you have a cluster of rotating barrels.
And what the ... electric motor is doing is rotating that cluster of barrels,
which then in turn mechanically operates a feeding system.
So what does this chain gun allow you to do that a regular machine gun can't?
Well, the big thing is reliability.
If you get a dud round in a regular machine gun it's going to go "click" instead of bang,
and then you're going to have to fix the system somehow.
You're going to have to manually cycle the action, usually that's enough.
Maybe if something's deformed you have to ... do something to clear the gun.
In a mechanically operated gun, whether it's a chain gun, or a Minigun, a rotary Gatling gun,
the action continues to cycle whether the cartridge fired or not.
So if you have a dud round, the whole round just gets extracted out,
and then thrown out the ejection port, or ejection tube, whatever it is.
Because that cycling of the gun is not dependent on energy coming from the firing of the cartridge.
This is the primary benefit of externally driven guns.
They are for situations where either a malfunction is immediately really bad for the operator,
or a situation where you simply don't have access to the gun to clear it.
Or, where we see this the most, is a situation where ... the gun is so big
that it's not practical for a single operator to actually clear it.
So these advantages come into play with things like helicopter mounted guns.
Well, if you have an AH-64 Apache, you've got a 30mm gun hanging off the bottom of the helicopter,
if you have a dud round you can't go climb out there and clear it.
So either you have an externally driven system like a chain gun that can clear it by itself,
or if you get a dud round you're done using that gun
until you go back to base and have a mechanic fix the gun.
A situation where you could have a really serious impediment
to the mission from a single dud round.
On an infantry machine gun if you get one dud round it's not that big a deal,
you just cycle it, clear it, and continue about your business.
The second place where this is relevant are the really large calibre guns.
We tend to see externally driven guns, especially chain guns,
in 20, 25, 30mm calibres where ... there's so much power in these cartridges
that if you had to manually cycle the thing
it would be extremely difficult to do so, even if you had physical access.
A good comparison to take note of here is
like the 20mm Oerlikon guns from World War Two which were recoil operated.
But if you had a misfire of some sort, in order to re-cock the gun
you basically had to hook a strap to the front end of the barrel,
and then use all of your body weight on the back end of the gun as leverage
to crank the bolt back to re-cock it.
You get above 20mm and it becomes basically impossible to do that sort of operation
with just plain human muscle power, you need a mechanical assist to do it.
And that's when the thing's like mounted on a naval mount where you can actually access it.
If you put this on an airplane or a helicopter, obviously you can't get to it.
... Well, there's one other place where this is relevant.
I said that you can control how long the bolt stays locked after the cartridge fires.
One of the things that that allows you to do is dramatically reduce
the amount of propellant gas that comes out of the breech.
If you hold that bolt closed until well after the bullet has left the muzzle,
which is a very short period of time in human terms,
we're talking how many milliseconds is the thing closed.
Well if the pressure has dropped a lot by the time you open the bolt,
there's ... very little gas left in the breech of the gun that can come out the back to, say, the firers.
This is a thing that's of value for, for example, a ... coaxial tank machine gun.
Where if you have a lot of gas coming back out of the gun
it's going to fill up the crew compartment of the tank, and that's going to be bad.
By deliberately delaying the opening of the bolt
you can minimise the amount of gas that comes back.
And no coincidence, one place where we see chain guns actually used by a major military
in just .30 calibre, one of the very few small calibre uses of them,
is in a couple of British AFVs that use essentially the Hughes EX-34 chain gun,
which in British service is the [L94A1].
And they use it as an armoured vehicle machine gun for ... a couple of the reasons here.
Because you can cram it in a corner where you don't have to have
easy access to clear it, because you won't need to.
And also to prevent the vehicle from filling up with noxious propellant gases.
So, those are the benefits that you're going to get.
Has anyone developed miniaturised chain guns?
Sort of. As I just said, Hughes has a .30 calibre one
that they've developed that is in military service. And it weighs about 30 pounds.
So it weighs a bit more than a traditional machine gun.
I should point out a couple of the advantages you do not get from a chain gun.
One of the big ones is rate of fire, a chain gun is a single-barrelled firearm.
And so even if hypothetically you could use this mechanism and get it firing really fast,
that one barrel is going to overheat, just like it would with any traditional firearm.
And so that's an area where if you want a very high density of fire, a very high rate of fire,
you are better off looking at a multi-barrelled rotary system like a Minigun.
Although it's worth pointing out that the actual number of seconds
you can fire a Minigun ... before it overheats is pretty much identical
to the number of seconds you can fire any other single-barrelled machine gun.
The Minigun has six barrels in it (the typical standard version),
but it's also firing about six times as fast as a traditional gun.
So each individual barrel is getting the same rate of fire through it
that you would get in say a 500 to 1,000 round per minute machine gun of any other design.
So the same number of seconds of firing gives you the same amount of heat in every barrel.
But you get a lot more bullets out there in a very short time period with a rotary gun.
Hence it's better for very high volume of fire, very short duration: things like aerial applications.
Anyway, chain guns don't let you fire faster necessarily.
What they give you is just that increase in absolute reliability,
protection from dud cartridges.
And there's also a benefit there if your ammunition is inconsistent,
you are not going to get malfunctions that come from an overloaded or under-loaded cartridge,
because again, it's not the power of the cartridge that's actually cycling the action.
It is an external independent electric motor that's cycling the action,
and doing it perfectly consistently every single time.
Alright, so the final part of the question,
are we going to see development of more man-portable chain guns?
I think the answer is probably no.
I could see development of them for unmanned purposes.
If you wanted to have a sentry type of gun that runs on its own sensors or remote control,
that's potentially a place where a chain gun is valuable
because you won't have a person there to fix it if something goes wrong.
And in those sorts of applications the absolute weight is probably not that important.
An extra 5 or 10 pounds, not a big deal.
For infantry use, I don't see this being something that's going to see more development
because I don't think the trade-offs are worthwhile.
In an infantry gun weight is a significant consideration
because someone has to carry the thing around, especially for a machine gun where
you also have to carry all the ammunition for it.
And you, by definition, have a person there who can fix a malfunction.
So if you could take an M240 (an FN MAG) and say,
"You'll be immune to reliability malfunctions from these specific causes
in exchange for adding 5 to 10 pounds to the gun. Is that worth it?"
I don't think the trade-off is there.
And I don't think it's really going to be possible
to make a Minigun lighter than a traditional machine gun,
because that traditional concept of using the cartridge
as the power source is a super cool, efficient idea.
I think we've all got very used to this concept, and people don't tend to realise
just how impressive it is that this is essentially a self-operating machine.
If you want to get rid of that and go to an external power source
there's a bunch of extra mechanical stuff that you have to put on the gun.
You're going to be able to get rid of a few bits, say a gas piston,
but most of the rest of the action components have to stay there.
You still need your locking system, you still need your bolt carrier.
You're still going to need your trigger mechanism.
Maybe the trigger mechanism can be simplified
because it'll probably be electrical at this point, but whatever.
But in exchange for this stuff you have to add in things like the chain.
And I have a hard time picturing a chain gun chain
that's going to weigh less than the gas piston that it's replacing.
So in theory the action can become a little bit shorter
because you don't have to have a recoil spring behind the bolt,
because the bolt's being pro-actively operated by an electric motor.
But of course now you have to add an electric motor into the thing too.
That's probably going to have some copper coils in it, that's going to be relatively heavy.
So I don't think you can make a ... .30 calibre or even a 5.56 calibre chain gun
... meet the same weight as a traditional machine gun.
Then of course you have to add in that you're carrying both ammunition and a battery,
instead of your ammunition being the battery.
So, with the exception of unmanned applications, I don't see it being that relevant.
Now for unmanned applications, if we're going to be talking about
putting something like this on a drone,
whether it's a ground-based drone or at some point an aerial drone.
That there's definitely consideration for, there's potential there.
Still weight would be an issue, so there would be a motive
to miniaturise, to lighten these things as much as possible, but that could actually happen.
Will we see guys carrying them around with a backpack of ammo and a feed chute,
and a battery strapped to their web gear? That I doubt.
Anyway, that was a really cool question Nikolas. I think ... once again that was a question that
there's a lot more that goes into answering it
than one might initially think, so that was a fun one to do.
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