The Plateau: Next Big Leaps in Small Arms Tech?

[Sturgeon]

Perhaps not exactly in-line with the OP, but one of the ideas that has come up recently, and been developed to a degree by GDLS, is the idea of a medium machine gun in a caliber intermediate to 7.62 and 12.7mm. GDLS has their LWMMG, some videos of which are below:

At first glance, the idea of a .338 Norma "bigger bullitt" dismounted MG sounds pretty stupid, but there may be a saving grace to the concept. Using larger diameter bullets (starting at about 9mm), you're getting into the range of a serious payload lobber, so launching a respectable-weight 9mm bullet (oh, say, 250 grains) at as modest a velocity as you can stand may be a good way to deliver penetrators, explosives, CS, and other fun materials to your enemies at a few hundred rounds per minute. If you go beyond inert projectiles (which just about necessitates a caliber increase over the .338 Norma), then the idea doesn't seem so silly if you can get system weight down enough.

I think this idea, to which one could say the GLDS LWMMG is a precursor, is a really interesting one, and I've talked before about how I think 9mm caliber in general is a good one for this sort of dedicated MG round.

I've been doing some ballistic models for a concept that would fire such a 250gr 9mm bullet of the same shape as the German wartime steel-cored SMK projectile at about 2,560 ft/s. This would necessitate a case about the same size as that of the .358 Norma Magnum, a considerably smaller cartridge than .338 Norma Magnum, perhaps putting this idea within the realm of feasibility for a dismounted weapon, especially if rate of fire could be kept below 500 rds/min. I think rate of fire similar to a Chauchat, actually, at about 250 rds/min, would be damn near ideal, putting this concept firmly between a conventional "inert" MG, and something like a grenade machine gun.

 

And, of course, it would probably do a number on ESAPI-equivalent plates, as well.

[Khand-e]

I'd argue that's the next big challenge. Currently, the US has never fought another country using peer body armor; it's too expensive for anyone but superpowers to use (a very comparable situation to Ancient Rome, and legionnaires' plate, in fact). What if we do? In that case, 5.56mm, 7.62mm, our whole suite of small arms ammunition below .50 cal is basically useless.

 

 

Perhaps not exactly in-line with the OP, but one of the ideas that has come up recently, and been developed to a degree by GDLS, is the idea of a medium machine gun in a caliber intermediate to 7.62 and 12.7mm. GDLS has their LWMMG, some videos of which are below:

 

 

*Tony Williams Voice*

 

"What we need is a general purpose armor piercing front line anti material machine rifle, .300 Winchester Magnum and .338 Norma and Lapua Magnum don't offer enough terminal effectiveness and have insufficient range against targets with Level IV plates, whereas .50 BMG is much too heavy and unwieldy on fully automatic sniper fire mode, with these cherry picked and rigged ballistic charts drawn from measurements and marketing claims I won't fully describe or explain, It's clear that the .408 Cheytac is an optimal round for a general purpose bullpup anti material auto sniper carbine, when shown here you can see it has more retained energy when fired out of the standard 72" carbine barrel at 2000m then .50 BMG Ball rounds, and will aid our soldiers in avoiding tragic situations such as those in Chechnya where our soldiers equipped with mere .300 Win mag and .338 Lapua rifles were hopelessly outranged by broken rubble building top volley fire tactics with 14.5x114mm KPV fire."

 

I probably could've done better but, reasons.

[Toxn]

If personal armor becomes a game changer, I suspect we'd see a greater use of HE and incendiary launchers.  If we can no longer kill you with single projectiles, we'll shred your unprotected bits with fragments, set you on fire, and stomp you with overpressure.

 

 

Sorted.

[Collimatrix]

I believe the final G11 caseless configuration basically uses a block of RDX. And I believe it, too, since that cartridge produces 5.45x39 levels of performance with a smaller diameter bore and less than 28 grains of propellant, and it's telescoped (which results in substantial propellant waste).

 

If you look at the first column of the table on page 5, you'll see that there are explosives that have drastically better energy density than RDX, unless I'm misunderstanding what ΔH_f means here.

 

I seem to recall that late Cold War Soviet shaped charges switched to higher brissance explosives, and had massively better performance because of it.  They went from ~450mm RHA pen on the late 2A21 and M62 to completely nutso insano 800+mm on the 3BK-29 125mm projectile:

 

This is the improvement in penetration in a shaped charge from switching from HMX to CL-20:

 

 

 

So there appear to be considerably more energy dense propellants available than what are being used.  I suspect it's a threefold problem of cost, speed of sound of the propellant gas, and not breaking the damn gun.  I also suspect that any improvement will be seen in heavier weapons systems first.  Right now they're receiving the love and attention before small arms are.

[Khand-e]

Clearly we need to get Comrade Mao-Xi Zhang back to my (unfortunate) youth city of Chicago to find a cheaper, more efficient method to manufacture HNC and ONC.

[Toxn]

There are considerably more energetic propellants than nitrocellulose that could be used.  I assume that either barrel materials or the speed of sound in the propellant gasses precludes their use.

So, speed of sound in a gas increases in an approximately linear fashion based on temperature. Further, the speed of sound is different for different gases (hydrogen >>> methane >> nitrogen > oxygen > carbon dioxide).

 

Given the above, the best you could do would be to select a propellant which runs at the hottest possible temperature and dope it with something that breaks down into lots of hydrogen and methane. This would obviously make life hell on barrels, which leads to the thought that part of the barrel should be in the form of an easily-removed liner.

 

Edit: finally, a good approach might be to try and go for an ECT - pumping in heat via a big electrode or whatever would allow you to explore faster propellant combinations than are presently available.

[Sturgeon]

So when I go without sleep for a while, I start getting daft ideas. Here's one!

First, I determined that to achieve parity in terms of energy with 5.56mm at 500 yards, you can use a .197" (4.85mm) 45gr bullet with a .92 i7 FF at 3,000 ft/s and get really close. So, now to try to achieve that with as little weight as possible. Let's entertain all the silly ideas at once.

Fuck nitro, let's go to some high energy HE based propellant, allowing us to have really small case volumes. The limiting factor here will be primer strength; guns can handle 120,000 PSI "just fine" possibly with minor design/metallurgy modifications, but the cartridge case heads and primers are a weak point. The case heads and probably be supported, and we'll wish away the primer problem. This is fun! 

So we now need an almost arbitrarily low case size. 5.7x28mm sounds like it should work (why not!), so we'll neck that down to 4.85mm and stuff the long, slender 45gr boolit into it. Huge, jacked up pressures will give us the 3 kilobuck velocity we're looking for. Cartridge weight will be approx. 5 grams.

 

Now, design a slick, P90-inspired bullpup to use it. Transverse-mounted mag should be able to hold 50-60 rounds, and total loaded mag weight will be .475kg, which is only a hair heavier than a 30-round USGI mag loaded with M855. 14.5" barrel, sure, why not. Extend the handguard beyond where it would be in a P90 for optics and ergos.

 

You end up with a plausible, albeit fictional little buzzgun with ballistics very close to that of 5.56mm but double the ammunition load. Add in a "smart" sight that compensates for wind drift and range actively, and you have something that would fit right in with the Ghost in The Shell franchise.

[Toxn]

So when I go without sleep for a while, I start getting daft ideas. Here's one!

First, I determined that to achieve parity in terms of energy with 5.56mm at 500 yards, you can use a .197" (4.85mm) 45gr bullet with a .92 i7 FF at 3,000 ft/s and get really close. So, now to try to achieve that with as little weight as possible. Let's entertain all the silly ideas at once.

Fuck nitro, let's go to some high energy HE based propellant, allowing us to have really small case volumes. The limiting factor here will be primer strength; guns can handle 120,000 PSI "just fine" possibly with minor design/metallurgy modifications, but the cartridge case heads and primers are a weak point. The case heads and probably be supported, and we'll wish away the primer problem. This is fun! 

So we now need an almost arbitrarily low case size. 5.7x28mm sounds like it should work (why not!), so we'll neck that down to 4.85mm and stuff the long, slender 45gr boolit into it. Huge, jacked up pressures will give us the 3 kilobuck velocity we're looking for. Cartridge weight will be approx. 5 grams.

 

Now, design a slick, P90-inspired bullpup to use it. Transverse-mounted mag should be able to hold 50-60 rounds, and total loaded mag weight will be .475kg, which is only a hair heavier than a 30-round USGI mag loaded with M855. 14.5" barrel, sure, why not. Extend the handguard beyond where it would be in a P90 for optics and ergos.

 

You end up with a plausible, albeit fictional little buzzgun with ballistics very close to that of 5.56mm but double the ammunition load. Add in a "smart" sight that compensates for wind drift and range actively, and you have something that would fit right in with the Ghost in The Shell franchise.

Idea for high-pressure primers: internal primer + electrical ignition through a lead going through the base centre. Case itself is used as the other electrode.

[Belesarius]

We got some smart folks on this forum.

 

Sounds pretty workable to me.

 

David Weber/John Ringo use electrical ignition in a 'big game rifle' of the future in the Empire of Man series.  I remember thinking at the time that I read it that it sounded remarkably plausible even now.  As in, if I saw one released, I wouldn't be overly surprised.

[Sturgeon]

The objection I've seen raised against electrical priming is its sensitivity to electronic "noise", which could conceivably detonate an electrical primer. Now, how likely that is, and what any possible workarounds may be, I do not know.

[Toxn]

Large spark gap plus relatively insensitive primer will help. Test it using some poor fool, a dry shag rug and a door handle.

[Khand-e]

I can see it all now though, the wave of the future.

 

-H&K gathers the knowledge of how to manufacture ONC or HNC from the University of Chicago.

 

-They make a new wundergun that, aside from not working in any way at all, uses a caseless, electric primed round with a propellent consisting of 100% HNC.

 

-The guns have an average lifespan of 1 round, oddly enough, so do the testers after trialing it.

 

-Germany is praised by people who don't actually shoot guns on how amazing and innovative their arms industry is and how people who hate on the new wundergun are merely misinformed and if it's so bad why did so many countries who never fight wars buy the wundergun HUH?!

[Collimatrix]

So, speed of sound in a gas increases in an approximately linear fashion based on temperature. Further, the speed of sound is different for different gases (hydrogen >>> methane >> nitrogen > oxygen > carbon dioxide).

 

Given the above, the best you could do would be to select a propellant which runs at the hottest possible temperature and dope it with something that breaks down into lots of hydrogen and methane. This would obviously make life hell on barrels, which leads to the thought that part of the barrel should be in the form of an easily-removed liner.

 

Edit: finally, a good approach might be to try and go for an ECT - pumping in heat via a big electrode or whatever would allow you to explore faster propellant combinations than are presently available.

 

Pretty sure the speed of sound in a (ideal) gas is proportional to the square root of the pressure:

 

Where c is the speed of sound, gamma is adiabatic index, p is pressure and rho is density.

 

There are a number of ways to cheat here.  You can use a two stage gas gun and separate the propellant gas from the energy source (vaguely analogous to what a nuclear thermal rocket does to increase Isp.  T___A found pictures of what (Sturgeon convinced me) were an experimental Soviet anti-tank two-stage gas gun intended for mounting in an ISU-152 and other AFVs.  The slightly less sophisticated combustion light gas gun has received some attention in the US of late.

 

ECT is a possible approach, and one that seems to command a lot of enthusiasm from the NationStates set.  To my eye there are some pretty glaring issues.  The first is that you're using electrical energy to heat the propellant gas, so you're running right into the same problem railguns have; the piss-poor energy density of stored electricity.  The second problem is that you're throwing the additional energy into the gas near the end of the power stroke, which isn't efficient.

 

My favorite approach is the travelling charge design, where a blob of propellant is attached to the base of the projectile.  The grain of this propellant is engineered to burn and produce most of its pressure once the projectile is a ways down the tube.  This is a spiritual relative of rocket-assisted projectiles and scram cannons.

 

The objection I've seen raised against electrical priming is its sensitivity to electronic "noise", which could conceivably detonate an electrical primer. Now, how likely that is, and what any possible workarounds may be, I do not know.

 

It's called HERO; Hazards of Electromagnetic Radiation to Ordnance.  It seems to be a problem mostly in a naval context where there are ginormous radars that have enough output to induce a current in an electrical primer.  Tanks and (land-based) aircraft have been using electrically primed ammunition for decades, and seem to get away with it.  Indeed, all German WWII tank guns used electrically primed ammunition (which rendered KwK 36 and 8.8 cm FlaK ammunition non-interchangeable...).

[LostCosmonaut]

Crazy idea: APFSDS round fired by a scram cannon, where the penetrator forms part of the inlet geometry.

[Khand-e]

APFSDS fired from 88mm L/56.

 

All modern tanks rendered obsolete.

[Toxn]

Pretty sure the speed of sound in a (ideal) gas is proportional to the square root of the pressure:

 

Where c is the speed of sound, gamma is adiabatic index, p is pressure and rho is density.

 

There are a number of ways to cheat here.  You can use a two stage gas gun and separate the propellant gas from the energy source (vaguely analogous to what a nuclear thermal rocket does to increase Isp.  T___A found pictures of what (Sturgeon convinced me) were an experimental Soviet anti-tank two-stage gas gun intended for mounting in an ISU-152 and other AFVs.  The slightly less sophisticated combustion light gas gun has received some attention in the US of late.

 

ECT is a possible approach, and one that seems to command a lot of enthusiasm from the NationStates set.  To my eye there are some pretty glaring issues.  The first is that you're using electrical energy to heat the propellant gas, so you're running right into the same problem railguns have; the piss-poor energy density of stored electricity.  The second problem is that you're throwing the additional energy into the gas near the end of the power stroke, which isn't efficient.

 

My favorite approach is the travelling charge design, where a blob of propellant is attached to the base of the projectile.  The grain of this propellant is engineered to burn and produce most of its pressure once the projectile is a ways down the tube.  This is a spiritual relative of rocket-assisted projectiles and scram cannons.

 

 

It's called HERO; Hazards of Electromagnetic Radiation to Ordnance.  It seems to be a problem mostly in a naval context where there are ginormous radars that have enough output to induce a current in an electrical primer.  Tanks and (land-based) aircraft have been using electrically primed ammunition for decades, and seem to get away with it.  Indeed, all German WWII tank guns used electrically primed ammunition (which rendered KwK 36 and 8.8 cm FlaK ammunition non-interchangeable...).

I was just extrapolating straight from this sort of graph:

 

 

Per light gas guns, I actually had a go at designing a self-contained cartridge for one years back (for a dumb idea about a hypervelocity small arm).

It was enormous -  30cm+ case length (including charge, plastic piston, gas chamber and burst disc) to launch a fiddly little flechette. But man that thing would have moved.

 

For ETCs you do indeed have the same issues with energy density as rail guns - although a bit less severe as the electrical component is merely functioning as a booster for the main charge. Interestingly; I remember reading some research that seemed to show that the best approach was to use one chemical charge (presumably something like a shaped charge) to produce a plasma ignition jet, which would then go on to ignite and boost the main charge. I don't know whether this was ever implemented seriously.

 

Travelling charge sounds interesting, but obviously you'd have to control the geometry of your blob thingy very well.

 

Do we have any people here who can do some preliminary research? Like; they have the wherewithal to load their own cartridges and measure bullet speeds, and have a gun they are okay with blowing up in the name of science?

[Toxn]

Via one of the Nathans:

http://www.thefirearmblog.com/blog/2015/10/23/3d-printed-portable-rail-gun/'>http://www.thefirearmblog.com/blog/2015/10/23/3d-printed-portable-rail-gun/

This says it all, really. With present tech you can make a weapon which is barely capable of being held, strips a significant proportion of the mass of the projectile off when fired and achieves velocities/energies in the range of a homebrew air gun.

[Toxn]

More rail gun malarkey:

 

https://www.youtube.com/watch?v=vAs9EHtKfVc

 

https://www.youtube.com/watch?v=KMT97bqaOdM

 

https://www.youtube.com/watch?v=_30BSXzb4Mo

 

A car full of capacitors don't get you much over the paintball gun you started with, it seems.

 

More DEW:

 

https://www.youtube.com/watch?v=dvrQciFL0ig

 

https://www.youtube.com/watch?v=oTLCHKb20zI

 

HAHAHA IT WAS ACTUALLY A HOAX

 

Have a laser instead:

 

https://www.youtube.com/watch?v=iVrJUbeuG44

[Toxn]

Holy fuck, plasma weapons might be into real after all:

 

[Toxn]

Holy fuck.

[Belesarius]

That's a rather in depth discussion.  If I'm reading that right, we could pretty easily have effective vehicle borne lasers pretty quickly.  I suspect that ship borne lasers are going to rapidly become a thing over the next few years.  I suspect air defence will be the primary focus of development, but then again, I know jack about high energy physics.

[Toxn]

That's a rather in depth discussion. If I'm reading that right, we could pretty easily have effective vehicle borne lasers pretty quickly. I suspect that ship borne lasers are going to rapidly become a thing over the next few years. I suspect air defence will be the primary focus of development, but then again, I know jack about high energy physics.

Yeah, but an actual Soviet laser pistol! With an excitation mechanism that practically begs to be scaled up and automated!

We could be making laser gatling guns right now, people. Right. Freaking. Now.