Silenced weapons

[Morte]

I've been thinking about futuristic silenced weapons, and I wanted to float a few ideas to see what people think. I don't know too much about this, so I'd value knowledgable input.

First up, what do we want from the weapon? It seems to me that we need it to be:

- Silent (doh).
- No/minimal muzzle flash.
- Usable from concealment, with range 200m+.
- A reliable killer, to prevent alarms.

We won't try to penetrate body armour. That's too ambitious for a silenced weapon.


Sticking with slug-throwers for the moment, I figure that....

- Silencing implies a subsonic projectile to avoid the sonic boom.

- Getting reliable kills implies a heavy projectile, to get the damage up at low velocities, and some sort of spreading/fragmenting/tumbling bullet. This will create relatively high recoil for the damage done.

- If you've got functional tranq technology, add the lethal version of it into the projectile as a bonus. But I figure drugged fletchettes are no good since high velocity means a sonic boom. [Comments?]

- To provide the required accuracy and control subjective recoil, we're looking at a carbine/rifle format of medium weight with optical (night)sighting.

- The low velocity means a highly curved trajectory, so we need a built in invisible rangefinder and computing gunsight. Infra-red laser?

- With chemical explosives, you need a sophiticated mechanical silencer and flash hider to control the propellant gases.


So, how to build it?

For a TL8 chemical slug thrower, I imagine a purpose-designed round firing a subsonic projectile in the 10-15mm range. [Any thoughts on the projectile type? Ignore the current rules of war.]

I'm thinking the barrel should be just long enough to let the round complete it's acceleration, or perhaps a bit longer, so that the propellant pressure is dropping off when it leaves the barrel and enters the silencer.

[I understand some silenced weapons drill holes in the barrel and bleed gas off into a silencer wrapped around it, to bring muzzle velocity down. But I'm going for a purpose-designed round so I figure the silencer starts where the barrel stops. It might end up quite long, so maybe bullpup is a good idea.]

The choice of propellant, cartridge dimensions etc would aim for minimal subjective recoil and a reduction in pressure before the bullet exits. [Is this meaningful/possible? I don't know this stuff.]

I can't see why it shouldn't be semi-automatic, with a full automatic option for those days when surprise fails. But there'd be an option to have the breech stay closed after the next round, to minimise mechanical noise. Caseless ammo would be a bonus.


As TLs go up, you get HUD links and deadlier projectiles. At very high TLs, large bore subsonic gauss weapons take over.


Then there are lasers, in theory available from TL 9 onwards (I'm doubtful). Lasers are often portrayed as emitting a "crack" sound when fired. Does anyone know if this is true, and if so how loud it is, and whether it's avoidable?


Um, any thoughts, folks?

 

[Straybow]

Any laser is going to superheat a volume of air along the path, which is exactly how lightning creates thunder. A stuttered beam allows the heated air to disperse a little more slowly, but there is still going to be some sound effect.

For slugthrowers, armor penetration is still possible. There was some experimentation with "penetrator" rounds. The lead bullet is formed around a sharpened tungsten rod. As the bullet flattens it releases the rod, which retains a significant fraction of the bullet energy due to high density. Personal armor that stops the bullet will be highly stressed, and the rod will more easily penetrate.

IIRC it only takes 53 foot-pounds (72 J) of energy to cause a disabling wound. So less than 10% of the energy from a low velocity round carried through the armor can still be effective.

 

[Todg]

http://www.solsec.org/equip/weapons/grenade_projector.html

http://www.solsec.org/equip/weapons/peg.html

Here's food for though. It turns out that you can design a supersonic projectile that significatly reduces the supersonic 'crack', and it may even be possible to design projectiles that eliminate it.

Another possibility is weapons fitted with anti-noise transducers. For those unfamiliar with anti-noise, it is currently possible to block repetative noises by emitting an exact copy of the sound pulse, only inverted so it is 180 degrees out of phase. The two sounds cancel each other out. Theoretically, one could have a weapon fiteed with an anti-noise transducer that exactly canceled the noise of the weapon.

 

[Andrew Boulton]

My first choice would be a meson rifle, but they're a bit hard to find, so I'd go for either a laser (you can probably avoid the sound of fried air by using a different wavelength) or a gauss rifle firing subsonic explosive rounds.

Don't forget, everything (ie speed of sound) depends on the planets atmosphere.

 

[Morte]

Originally posted by Straybow:
Any laser is going to superheat a volume of air along the path, which is exactly how lightning creates thunder. A stuttered beam allows the heated air to disperse a little more slowly, but there is still going to be some sound effect.

Thanks for the info -- I must admit that I don't really want lasers to work. They're too easy. Designing the slug throwers is more fun.

For slugthrowers, armor penetration is still possible. There was some experimentation with "penetrator" rounds. The lead bullet is formed around a sharpened tungsten rod. As the bullet flattens it releases the rod, which retains a significant fraction of the bullet energy due to high density. Personal armor that stops the bullet will be highly stressed, and the rod will more easily penetrate.

Well, might as well use it if it's going to help. OK, the low velocity slug thrower includes a tungsten (or similar) core.

Here's a bit of fun:

 

[Morte]

Originally posted by Corejob:
http://www.solsec.org/equip/weapons/grenade_projector.html

I don't really believe that one -- why silence a weapon with an explosive projectile?

Silencing a low velocity projectile isn't that hard -- the De Lisle carbine in WWII (firing .45ACP) produced more noise from the firing pin than the muzzle, and that was a wartime rush design. I guess bagging the propellant gives a marginal improvement, and brings the size of the weapon down.

http://www.solsec.org/equip/weapons/peg.html

More like it. If you've got gauss weapons, the whole thing gets a lot easier.

Here's food for though. It turns out that you can design a supersonic projectile that significatly reduces the supersonic 'crack', and it may even be possible to design projectiles that eliminate it.

That would be very handy. If that pans out, we might end up with a reworking of your TL8 fletchette gun which is optimised to work with a silencer.

Another possibility is weapons fitted with anti-noise transducers. For those unfamiliar with anti-noise, it is currently possible to block repetative noises by emitting an exact copy of the sound pulse, only inverted so it is 180 degrees out of phase. The two sounds cancel each other out. Theoretically, one could have a weapon fiteed with an anti-noise transducer that exactly canceled the noise of the weapon.

Now this, as it happens, is something I do know about. I don't think a practical system could resolve the trade-offs between efficiency, size, weight, bandwidth and directionality at TL7-8. E.g. a horn-loaded piezo driver would be loud enough and light enough, and if you could set up the propellant to produce purely high frequency sound it could be small enough, but you'll never match the directional pattern of the muzzle sound.

TL 9, well, that's getting into "can't foresee" land.

 

[Todg]

Originally posted by Morte:
I don't really believe that one -- why silence a weapon with an explosive projectile?

Because the point of silencing the weapon is to conceal the firer. Ever seen the DBCATA round? It was a silent 40mm grenade. Pretty nasty when rounds start exploding among your people and you have no idea where they are coming from.

Totally silent weapons aren't going to fool anyone for long. As soon as someone falls over and there's a bullet hole, eveyone (who's reasonably intelligent) will know what is going on.

In general, the purpose of a silent weapion is to allow the shooter to fire without being detected. What happens on the terminal end is less important. By that time, the shooter is already slipping away.

 

[Todg]

Originally posted by Morte:
Now this, as it happens, is something I do know about. I don't think a practical system could resolve the trade-offs between efficiency, size, weight, bandwidth and directionality at TL7-8. E.g. a horn-loaded piezo driver would be loud enough and light enough, and if you could set up the propellant to produce purely high frequency sound it could be small enough, but you'll never match the directional pattern of the muzzle sound.

TL 9, well, that's getting into "can't foresee" land.

Which makes it ideal traveller fodder.

 

[Todg]

Originally posted by Morte:
Silencing a low velocity projectile isn't that hard -- the De Lisle carbine in WWII (firing .45ACP) produced more noise from the firing pin than the muzzle, and that was a wartime rush design. I guess bagging the propellant gives a marginal improvement, and brings the size of the weapon down.

It totally eliminates flash. Suppressors have a first round flash problem. Also, captive propellant systems are highly efficient. The general rule of thumb for suppressors of marginal performance is that you need 20x the volume of the barrel for the suppressor. That means that effective suppressors are big. Don't be fooled by the size of suppressors by GemTech and the like. Those suppressors are efficient for their size, but they aren't very quiet.

I've built quite a few suppressors, as well as designing a few rounds for them. If you want virtual silence, you need a big tube. DeLisle had it right.

http://www.guntech.com/stealth/index.html

http://www.guntech.com/suppressors/index.html

I don't have the latest version up. These include a new suppressor design and the .460 Stealth cartridge.

 

[Morte]

Originally posted by Corejob:
</font><blockquote>quote:</font><hr />Originally posted by Morte:
I don't really believe that one -- why silence a weapon with an explosive projectile?

Because the point of silencing the weapon is to conceal the firer.</font>[/QUOTE]Well, OK. I was thinking more in terms of shooting a lone sentry then moving undetected to the door he was guarding. I guess there are roles for both silent(ish) and noisy projectiles.

 

[Morte]

Originally posted by Corejob:
</font><blockquote>quote:</font><hr />Originally posted by Morte:
Silencing a low velocity projectile isn't that hard -- the De Lisle carbine in WWII (firing .45ACP) produced more noise from the firing pin than the muzzle, and that was a wartime rush design. I guess bagging the propellant gives a marginal improvement, and brings the size of the weapon down.

Suppressors have a first round flash problem.</font>[/QUOTE]Ah, that I didn't know. Thanks.

Also, captive propellant systems are highly efficient. The general rule of thumb for suppressors of marginal performance is that you need 20x the volume of the barrel for the suppressor.

Or that. OK, you convinced me.

Can a captive propellant system work with the sort of barrel length that's needed to shoot accurately at 200+ yards? And what about the mechanical side, I can imagine ejection being pretty tricky. [I was thinking of an electrically fired caseless round with my "Son of DeLisle" idea. This would remove firing pin and ejection noise, leaving loading which can be deferred by user override.]

I don't have the latest version up. These include a new suppressor design and the .460 Stealth cartridge.

Looking forward to it....

 

[far-trader]

Hmm, interesting. I know I saw this captured propellant round somewhere else only bigger. Foggy recollection of a recoilless rifle using it or something similar, but it may have been only a game treatment and not RealLife(tm)... ah yes, the Armbrust!

Here's a link to a GURPS treatment of it (scroll down the page)

GURPS TL7 Heavy Weapons

I used to have a link to a historical site that had the details of it but the link seems to have gone awol.

Hmm, an idea is cooking, or is it one I've had on the back burner finally getting some notice from this old brain

In either case, Corejob I wonder if you have some ballpark figure of just how much more bang for the buck a captured propellant round gets. i.e. how much of a gain over conventional rounds in terms of energy from the same propellant, just a ballpark % better would be fine since the design system I'll use is pretty sloppy anyway. Also any other issues like added cost of manufacture, weight, etc., if you know them off the top of your wondrous gunbunny head Thanks in advance.

 

[far-trader]

Originally posted by Morte:
Can a captive propellant system work with the sort of barrel length that's needed to shoot accurately at 200+ yards? And what about the mechanical side, I can imagine ejection being pretty tricky. [I was thinking of an electrically fired caseless round with my "Son of DeLisle" idea. This would remove firing pin and ejection noise, leaving loading which can be deferred by user override.]

I'm sure Corejob can offer a more authoritative answer but I don't think you can have a captured propellant and caseless round, they seem mutually exclusive. So you'll still have to deal with the ejection noise (vague memory of a captured spent round system used by SAS or some such). Electrically fired (ETC rounds iirc) propellant should work though so you can eliminate the firing pin ping.

One more note, with captured propellant you have to use a manual loading mechanism and reloading action (no gases to cycle the bolt), so no semi or full auto actions (at least not without some other power source).

 

[far-trader]

Just recalled this little gem too, the Teleshot for silent shotguns

 

[Todg]

Captive propellant rounds require a case, and captive propellant rounds are not efficient for small cartridges. There's a linit as to how small you can make the cartridge and still fit everything in. They become much better (and more efficient) for larger rounds.

The Russians developed several silent small caliber rounds.

http://world.guns.ru/ammo/sp-e.htm

The best knon of the US silent cartridges using captive propellant are the Teleshot, silent shotgun round mentioned by far-trader (thanks for the reference to my web site) and the DBCATA 40mm round (Disposable Barrel and Cartridge Area Target Ammunition) which was developed by AAI (the fine folks who also gave us Teleshot) during the Vietnam war. The cartridge not only used captive propellant, but also included its own stub barrel. The ropund was clipped to the front of a plate mounted on the rifle, and fired. The the remaining empty cartridge was simply thrown away. I'll post a photo of anyone is interested.

The captive propellant system is also used on the FLY-K silent mortar.

For small calibers, captive piston systems tend to be less powerful than their conventional rivals. As caliber increases, there is less of a difference, however, captive propellant system are restricted to low pressure applications for obvious reasons.

Because propellant gasses are totally encloses, there is zero flash and very little noise. They tend to be much more quiet than all but the largest suppressors.

Mechnical noise is a concern for ultra quiet weapons. For this reason, many are manually operated. One of the problems with the DelIsle was that the gun was quiet, but operating the action was quite noisy.

Gauss weapons (coil type) seem to offer the ideal package for silent weapons. Because coil guns do not require bore riding projectiles, there is little or no precursor wave generated as as the projectile compresses air in the barrel. Obviously, there is no expanding propellant gas.

For chemically powered weapons, there doesn't seem to be a real advantage for caseless weapons over conventional ones. Firing pin noise, and even action noise is a relatively small component. Also, there are designs that do quite well at silencing mechnical noise, and even caseless guns have a feed cycle, so they don't eliminate mechanical noice.

One possibility might be to have a silenced MetalStorm type weapon. That would eliminate mechanical noise. Other noise sources could be dealt with in the conventional manner.

 

[kaladorn]

Corejob raised a subtle point. By higher TL, it seems likely to me that your Battle Armour will have built in active systems which will be able to instantly backtrack projectile weapons. The passive systems would use sound or visual on the rounds trail-through-atmosphere. Active systems would use top end radar. Seems like this would make backtracking projectile weapons attacks pretty basic by TL15.

On another point, unrelated, but for Corejob:
Have you done one of those barrel-end shotgun attachments for ARs yet? Used for point-men, they are some sort of fire-through grenadelet that is used to quickly engage any ambushing force to give the ambushed force time to get into their 'actions on/immediate action' routine. I've seen them for the C7/M16. They seem like a relatively quirky but interesting unit and possibly quite useful for urban combat too. Giant shotgun, more or less. Then it's back to the AR.

 

[Todg]

Above is the DBCATA (Disposable Barrel and Cartridge Area Target Ammunition) silent 40mm grenade as developed by AAI. The device is a self contained grenade and launcher. A simple launcher plate can be affixed to any number of weapons As noted previously, the DBCATA is relatively silent, flashless and smokeless.

 

[Todg]

Originally posted by kaladorn:
On another point, unrelated, but for Corejob:
Have you done one of those barrel-end shotgun attachments for ARs yet? Used for point-men, they are some sort of fire-through grenadelet that is used to quickly engage any ambushing force to give the ambushed force time to get into their 'actions on/immediate action' routine. I've seen them for the C7/M16. They seem like a relatively quirky but interesting unit and possibly quite useful for urban combat too. Giant shotgun, more or less. Then it's back to the AR.

I'm not sure of the utility of such a weapon, since unless the ambush has very few people, they'll be too spread out for any such weapon to have much effect. Most people fail to realize that they typical shotgun pattern is less than a foot wide at 25 feet. Even cannister loads for the M203 aren't that effective, although soldiers perceive that they are. (if you were to believe television, someone armed with a shotgun, even if they had the eyesight and coordination of Mr. McGoo, could take out the entire front line of a pro football team.

Something like a full auto shotgun is another matter, however there is just no good solution to being caught in an ambush except to charge the source of fire and hope for the best.

 

[Todg]

If you are looking for a silent killer, what about something like a microwave weapon that can bake a target's brains silently and from a distance? Surely there is some solution other than projectile weapons.

 

[Morte]

Originally posted by Corejob:
If you are looking for a silent killer, what about something like a microwave weapon that can bake a target's brains silently and from a distance?

Assuming you could focus and direct the microwave radiation, I wonder how it would fare in rain -- the intervening water might act as pretty good "armour".

Surely there is some solution other than projectile weapons.

One would like to think so. But I'm struggling.

Lasers, obviously, though I don't really believe in laser rifles until we get into TLs where everything is a handwave. Perhaps a laser designator guiding in a fletchette cloud dropped from a stealth UAV.

Um, if the breeze is right and you can get reasonably close, there's gas.

I'm not doing very well here.