Feasibility of "in situ" ammunition production and salvage

Question

In a (relatively) near future setting, several factions scramble to militarize as civil unrest on their planet turns into civil war. Factories are reprogrammed and prototypes sent to the front, guns blazing, in an effort to preempt the opposition. Without a large stockpile of ammunitions, however, those guns are about to run dry. How do we prevent that?

Background

A typical "heavy armor company" consists of 3-5 large vehicles (for the sake of this question, let's say two main battle tanks, one heavy artillery and a recon aircraft) with an individual mass of up to 120 tons, supported by a convoy of transport and engineering vehicles, a few drones, power armored infantry and lots of support personnel.

The company has the ability to perform extensive repairs and/or modifications, provided that spare parts are available. Anything but minor repairs requires a hangar and some stationary equipment (think airliner maintenance). However, vehicles can be refueled and rearmed in the field, if necessary.

New vehicles, weapons and spare parts are made in large factories and sent to the front via convoy. However, since production cannot keep up with losses, most companies rely in part on field salvage and black market trade to remain operational. Vehicles are fairly modular, so removing e.g. a capacitor bank from a wrecked tank and installing it in your own is possible.

In a pitched battle, a single vehicle can use up to five or six tons of ammunition, hopefully taking out multiple targets in the process.

Notes on available technology:

• Most vehicles above 20t carry a miniaturized nuclear (or similarly effective) power source.
• 3D printing, advanced materials and limited nanomachines exist.
• Rapid iterative design is common in the production of vehicles and other high tech goods, which increases flexibility and design quality, but may limit output.
• In addition to conventional weapons and railguns, directed energy weapons and electronic warfare are effective tools in combat.

Factors that make ammunition more scarce:

1. This society is already pretty good at making (civilian) vehicles. They've just started producing weapons and ammunition on a relevant scale.
2. Point defenses and active protection systems are very common, so a single shell or missile is likely to be deflected. To stop a tank, you fire volleys.
3. Anti-air and anti-orbital defenses, which rely on specialized missiles and extreme velocity shells, will get resupplied before ground vehicles. Losing a few tanks is acceptable, a ballistic missile strike on your factories is not. Directed energy weapons lack the range to serve an anti-air role.

My Question

Considering the above circumstances, would it make sense to salvage and/or produce ammunition between battles or does a company have to rely entirely on supplies delivered from the factories? Would it at least be feasible to re-produce simpler ammunition types (e.g. railgun projectiles)?

Answer 1

A lot of assumptions are missing in this question, so the answer is actually "it depends".

If weapons are electromagnetic railguns or coilguns, then portable 3D printers could theoretically make the rounds so long as a suitable material is available to feed them (and a suitable power supply is also available). The Quartermaster might have some sort of mechanism to grind salvaged metal into the powder form for the 3D printer, and a "sifting" mechanism to separate out materials which are unnecessary or harmful to the process. As a bonus, lower performing rounds can be produced if there are shortages of the correct materials, imagine a metal "can" full of dirt or concrete, with the metal being used to provide something for the magnetic or electric fields to grab onto, while the fill provides mass for a kinetic energy attack.

If you are using conventional ammunition, then the problem is insurmountable in the field. Ammunition is a system with multiple parts, all of which need to be made to fairly high precision, otherwise you will have issues with feeding the ammunition, reliable firing and even ballistic performance of the rounds. While you "could" make it using a 3D printer, the process would be painfully slow, and require you have access to lots of different materials to manufacture all the different parts. In the time you "print" one round in the field, a factory could produce hundreds or even thousands of conventional rounds (depending on calibre etc.)

A similar calculus will be in effect when looking at other logistical supplies, from food, to fuel to spare parts.

In WWII, we saw a fairly extreme example, with the Western allies choosing to build relatively simple, rugged vehicles (like the Sherman tank) while the Germans chose to build much more complex, expensive and ultimately unreliable vehicles (like the Panther). A Panther broken in the field would need to be recovered and often sent back to a second or third line depot to replace a broken transmission (a common fault), while a Sherman was much less prone to these sorts of breakdowns, and could often be repaired in the field.

The other issue in logistics goes right back to the manufacturing. The German industry was not well organized and eventually suffered breakdowns in production and the ability to ship units to the front (much less other issues of feeling and manning the advanced equipment), while the Western allies continually built their manufacturing base to the point that the Willow Run assembly plant was producing entire B-24 Liberator bombers at a rate of 1 every 24 hours (and this was a large, 4 engined bomber). Similar production rates were happening with tanks, trucks, cargo ships...you get the idea.

It seems very surprising that your fictional nation is unable to ramp up production to the needed extent, but perhaps like WWII Germany or post war USSR you have a command economy which focused on the "sexy" fighter planes and tanks, while ignoring transport trucks and other more mundane elements of the fighting force. They are going to have to convert to a wartime economy very quickly; or else...

Answer 2

The enemy gets a vote, too

When the enemy discovers you scavenging to re-use ammunition, they will promptly start booby-trapping it.

Then some clever enemy will begin seeding your scavenging areas with slightly mis-sized ammunition, so you damage your own weapons upon use.

The process of scavenging and recycling, say, railgun projectiles will require additional workforce in the most dangerous and most expensive locations possible. That workforce seems likely to increase (rather than decrease) your support requirements - all those technicians need food, security, energy, and ...thanks to the booby traps... special equipment and medical care.

Any kind of war manufacturing within range of enemy detection will quickly draw enemy attention as a high-value target, and enemy recon will immediately seek them out. Since the mass and volume of inputs to a manufacturing process tend to be vastly greater than the outputs, forward manufacturing will require many more convoys of input materials...all of which need to be crewed and protected and supplied.

Finally, there's a strategic problem: Historically, running-low-on-ammo usually means that you have outrun your supplies, and it's time to go on the defensive until your supplies catch up to your troops. Generals keep an eye on next week's supply estimates because it influences today's actions. Scavenging resources from the battlefield is great, but it seems unpredictable, and therefore prone to influence a more conservative (and longer) campaign.

Answer 3

If you're salvaging and making ammunition on the front lines, you're losing.

Perhaps because you've lost the home factories or because the home factories are now on the front lines. Purpose built factories can put out ammunition at higher qualities and quantities than anything you'll be able to make do and mend at the front.

It's possible that this is an apocalyptic scale war and that everyone is losing and they're all doing this, but if it's just you and everyone else's logistics can bring supplies from home, you're losing.

It sounds like your logistics are failing. You're trying to shorten your supply lines.

Traditionally that's done by retreating, given that the other option is to run out of bullets and either surrender or die, it may be better to order the retreat.

Now may be a good time to sue for peace

If both sides are resorting to this, a cease fire may be in order before your front lines resort to throwing rocks at each other. It's generally considered a good time to end a war if neither side can afford to keep it going. If it's just you...

Answer 4

I agree with Separatix's answer. Your armies are already in the process of losing because their logistics isn't keeping up. Napoleon is credited with saying, "An army marches on its stomach." Logistics is not a side aspect of war. It is a central aspect which permeates every decision a competent military. If your military isn't thinking this way, it probably isn't competent enough to manufacture ammunition.

Speaking of which, if you can't supply ammunition, its also highly probable that you can't provide gasoline either. Your armor is going to be stationary very soon. If you have the logistics for gasoline but not ammunition, then that suggests there's a deep rooted issue with your nation's manufacturing of ammunition. You'd have to explain why the ammunition is manufacturable on the battlefield, but not easy to manufacture at home. Something about the battlefield makes it possible.

Some ammunition is manufacturer. I have personally reloaded handgun rounds. It's a pretty straightforward process. I bought my bullets. You can make them from lead yourself, but making full metal jacket bullets requires hardware I didn't have (but a military could). I bought the gunpowder and primers. I recycled my own brass (handgun brass can be recycled a large number of times. Rifle brass starts to stretch from the stresses).

By a giant margin, the most difficult piece to manufacture in situ is the primer. This is the small cylinder of impact-sensitive explosives that sets the main charge off. The materials used in this are not fun to create. Mercury Fulminate was popular for a long time, but there is an effort to try to get mercury off the battlefield. These are typically cast into carefully shaped brass containers. Their shape is critical. They need to fit snugly into the round, and have the right mechanical properties such that when the firing pin strikes them, they explode. At the very least this calls for a full chemical engineering factory and brass swaging equipment. And some soldiers with really steady nerves -- I would not want to be anywhere near incompletely packaged primers.

The gunpowder is easier. It's only nitrocellulose or similar compounds for handguns. RDX and related explosives do appear in the larger rounds. These are nasty compounds. Making nitrocellulose, for example, calls for nitric acid, which is not something I would feel comfortable transporting to the front lines, and I don't think you could make it. So it's still a pain, but you may have some options. If everyone is using the same explosive for propellant, you may be able to canabalize others.

Indeed this is probably your best chance. If you canabalized all of the materials, you might be able to "rechamber" a round to fit your barrel.

However, this is ignoring the reality of vehicle combat. I don't know any stats about your 120 ton vehicle, but the M1A2 Abrams is 65 tons, so you're talking about vehicles on the same order as Abrams. So if you want to penetrate one with your weapon, you're going to probably need something on the order of the kind of bullet the M1A2 fires. Meet the M829:

This beast is going to be trouble to manufacture. It's a depleted uranium round, which means you're going to need the capability to machine uranium. That's nasty stuff to machine, especially without dosing all your soldiers with toxic uranium dust. Perhaps you could have the bullet itself be shipped from the nation, and cobble together the rest on the front lines?

3d printing may give you options, but it is as of yet unclear whether it will be the silver bullet you need. The military is very interested in 3d printing materials used in war, but they haven't yet reached the point where we can say if its feasible or not.

In the end, the real answer is going to be the same one all real armies have: "Use less ammo if you're running out!" Real armies adapt to the reality of warfare. B

Answer 5

Another problem with your question is "Factories are reprogrammed".

That worked in WW2 because:

1. the weapons were pretty simple,
2. factories weren't as specialized, and
3. the US started preparing more than a year before Pearl Harbor, due to Cash-and-carry, Lend-Lease, and foresight that the US might get dragged into the war whether we wanted to or not.

Answer 6

As others have said, manufacturing classic modern ballistic ammo in the field won't work very well.

But the directed energy weapons will be able to resupply in the field, so if that's critical to your story, make them the focus. You can have a couple different types of energy weapons w/ different power requirements & a couple available types of fuel & generators. For instance your shortest pulsing lasers can run off their own capacitor banks driven by any generator or even batteries, but something else could operate more like a particle accelerator & may require more power, so only nuclear & massive combustion power plants will drive it (you could work that into an explanation of 120ton vehicles, maybe, by making them elongated to support a linear accelerator type weapon)