Wanted -- T20 Stats for a Hollywood SMG

[Linwood]

There's a movie called "Deep Rising" that was on cable earlier this week. I don't know that I'd recommend it to anyone (pretty standard monster from the depths eats everyone sort of thing), but the main characters were toting around some weapons that would be pretty cool for Traveller characters.

From what I can recall, the guns were roughly assault rifle-sized, fairly small in caliber, and had 5 or 6 barrels in a Gatling-style arrangement. They are obviously something created in a movie prop house somewhere (they would have needed a truck to haul all the ammo they used up, for one) and probably aren't feasible in today's real world, but might make an interesting TL 9-10 weapon.

Any thoughts on what game stats (preferably T20) might be for something like this??

 

[tjoneslo]

As a wild guess, first pass:

Cost: Cr2,000
TL:9
Weight: 3.5kg
ROF: 20/100
Range 45 meters
DMG: 1d8 (x2)
Size: Medium
Type: Piercing
Recoil: Yes
Ammo: 1000 rnds, 8kg, Cr3,000
Ammo: 100 rnds, 0.8 kg, Cr300

This uses a very small caliber caseless round. It makes up for it's lack of penetrating power and round size by pure rate of fire. (ROF 20 adds +5 dice, ROF 100 add +10 dice). User has a choice of a smaller 100 round magazine for portable firepower or a larger, back mounted belt feed with a base 1000 rounds and a cability to chain belts to as many as required.

 

[Linwood]

I like it!! Thanks!

Now all I have to do is find a way to work it into the campaign...

 

[montanakennedy]

One of the little side-effects of chain guns is that there is no "belt" of ammo. The rate of fire precludes the use of a solid or disintegrating-link belt. The case that contains the ammo holds the cartridges in such a manner as to allow them to feed mechanically - usually a series of powered ratchets/rollers helping with the feed.

Dave

 

[Linwood]

Then a significant portion of the loaded magazine weight for a true chain gun would be the magazine itself, since it would be more complex mechanically than a simple box-type clip. So maybe the 1000-rd backpack should weigh an extra kilo or so (and maybe cost a bit more) to reflect that.

 

[Todg]

Originally posted by montana kennedy:
One of the little side-effects of chain guns is that there is no "belt" of ammo. The rate of fire precludes the use of a solid or disintegrating-link belt. The case that contains the ammo holds the cartridges in such a manner as to allow them to feed mechanically - usually a series of powered ratchets/rollers helping with the feed.

Dave

It should be noted firstly, that the original poster described a 'Gatling type' gun, a weapon with multiple barrels each with its own dedicated bolt. This is a significantly different weapon than a chain gun, in which a single barreled weapon is operated via an electrically or hydaulically powered chain attached to the bolt. It is a common error to confuse the two.

Secondly, both chain guns and powered Gatling guns (known variously as revolving canon or mini-guns) have used both linked and linkless feed ammuniton. Linked ammuniton has proved to be troublesome in revolving guns with rates of fire over 4000 round per minute, and in general linkless feed has supplanted linked ammunition in these guns. Instead, the ammunition is carried in 'conveyer elements' that are part of the feed system but are analogous to links except that they surround but do not grip the ammunition.

Chain guns have significantly slower rates of fire, and may or may not use linked ammunition depending on whether there is room for a linkless feed system.

An explanation of the operation of the chain gun can be found at http://www.rkba.org/guns/principles/operating-systems/chain.html , that of the Gatling gun at http://www.rkba.org/guns/principles/operating-systems/gatling.html

For more detailed information (i.e. of interest only to fanatics), See Chinn's "The Machine Gun"

 

[Todg]

Just for the fun of it, and not having see the movie you refer to, here's my own version of the concept. I originally envisioned a rifle/minigun hybrid that would fire the same ammunitions as the FN P90 PDW. This is a smaller and less powerful version of an assault rifle cartridge, but still considered effective out to 300 meters.

The idea was to have a weapon that could saturate an area at reasonable ranges but still be controllable. I photoshopped up a picture to go with it:

Unfortuantely, I don't use T20 so I can't help with stats.

 

[kaladorn]

You may say it is based on the FN, but when I look at that (cool picture, mind you, can I 'borrow it'?), it screams SA-80 as the base.... (just in terms of appearance).

 

[Todg]

Originally posted by kaladorn:
You may say it is based on the FN, but when I look at that (cool picture, mind you, can I 'borrow it'?), it screams SA-80 as the base.... (just in terms of appearance).

Sorry. Perhaps I was not clear. The the concept for the weapon was to build it around the cartridge used by the FN P90 (5.7x28mm). The SS190 generates a modest 514J of energy, but in a proposed weapon of about 5.5 kg will generate a recoil energy of about 1J. Low recoil energy is important when you add up all the recoil for a weapon with a rate of fire up to 3,000 rpm.

The composite photo was made from a GE minigun, SA-80 and FAMAS rifle. You can find more photos at http://weapons.travellercentral.com You are welcome to use any that interest you.

 

[Linwood]

Great picture, Corejob -- other than the telescopic sight (the movie guns used trapezoidal-shaped iron sights) it looks very similar to what the Hollywood FX guys dreamed up.

(Well, they didn't have the ammo conveyor either, but that's Hollywood...

)

And that's a pretty impressive website that you're building!

 

[Straybow]

Only 514J for the P90? I new it was low energy, but I didn't realize it was that low. You would need 3000 rds/min to be effective at 300m! I don't know why you'd need a telescopic sight, unless it is for surveying the damage.


I'm guessing it isn't a telescopic sight, but rather a heads-up "floating" sight. It just gives you a day-glo dot floating in the general line of fire as an artifact of binocular vision. Commonly used for combat shotguns.

 

[kaladorn]

They claim the FiveSeven (the pistol firing the 5.7mm round) will penetrate a PASGT helmet at 100m. So I'm not sure exactly how dangerous the projectile is once it gets into tissue, but it looks like armour is defeatable with this round.

And is that rating for the P90 for the little snubby self defence version with the snubbie barrel, or the full length (if this could truly be said to apply to the P90....) barrel?

 

[mike wightman]

Both the P-90 and HK MP-7 claim to be able to penetrate NATO body armour out to 100m for the P-90 and 200m for the MP-7.
The P-90 barrel length is 263mm, while the MP-7's is only 180mm.
I'd be interested to see if the bullets tumble in a wound.

 

[Todg]

Originally posted by Sigg Oddra:
Both the P-90 and HK MP-7 claim to be able to penetrate NATO body armour out to 100m for the P-90 and 200m for the MP-7.
The P-90 barrel length is 263mm, while the MP-7's is only 180mm.
I'd be interested to see if the bullets tumble in a wound.

It should be noted that what US troops are currently wearing is not NATO armor, and that the hemets has been much improved in terms of ballistic protection.

The latest military vests, with inserts, are capable of stopping a .30 caliber armor piercing round fired at point blank range. The latest helmets approach that. I have see photos of more than one helmet that took multiple AK rounds.

One of the growing concerns in military circles is that the latest body armor is imperious to current rifle rounds. Indeed, even going back to the more powerful 7.62x51mm won't help because this rounds is also stopped. This may give new life to flechette firing weapons, whose penetration far outstrips any conventional bullets. The big question is will the flechettes themselve prove to be lethal enough?

Steyr has reported that there has been a renewed interest in their flechette firing ACR, originally developed for the US Army ACR trials in the 1980s.

 

[mike wightman]

The data I am quoting from quotes penetration of CRISAT armour, helmets and vests with titanium and 20 layer kevlar.
Whatever that means?

 

[Todg]

Originally posted by Sigg Oddra:
The data I am quoting from quotes penetration of CRISAT armour, helmets and vests with titanium and 20 layer kevlar.
Whatever that means?

CRISAT armor is a NATO standard meant to simulate Soviet body armor. It is 20 layers of kevlar covered by a 1.6mm titanium plate. Soviet, or Now Russian, body armor is hardly state of the art.

According to FN, developer of the P90, Five-seveN and the 5.7x28mm round, "The SS190 will perforate 48 layers of Kevlar up to 200 meters when fired from the P90 and achieve the same result up to 50 meters with the Five-seveN handgun.'

They specifically not that the SS190 has less penetration that the SS109 5.56x45mm, which is equivalent to the US M855 round. This round (the M855) is one of the best penetrating service round, but is still stopped by a NIJ level IV vest.

I can only assume that if the SS190 has less penetration than the M855 and the M855 is stopped by a Level IV vest, then the SS190 will be stopped by the same Level IV vest.

The 5.7x28mm has superior penetration to the 9mm, the round it is meant to replace. But it has nowhere near the penetration of full powered rifle rounds, and these can and are being stopped by body armor currently in use in Iraq. The interceptor OTV with inserts, as issued to front line troops, is capable of stoping all known military rifle rounds upto and including 30 caliber amor piecing ammunition fied at point blank range.

 

[kaladorn]

Since you seem to be in the know, could you clarify a couple of points:

1. What is the extent of expected blunt trauma?
2. What is 'point blank range'? That is to say, has a bullet achieved its maximum velocity (I was led to believe not) before it has travelled some distance? Is point blank *actually* the highest threat?
3. How do specialized munitions affect this? Bulk ammo is probably not the best armour piercing out there... aren't there specialized rounds that might still go through interceptor? Would the new 6.8mm likely change the balance?
4. Where does Interceptor offer that level of protection? Head, front of chest, ??
5. In areas not covered with that level of protection, how much lower is the protection and will these rounds be effective?
6. Lastly, what's the weight on a full Interceptor system?

I'm just curious. I've seen allegedly bulletproof vests shrug off hits from pistols and SMGs, but be diced by jacketed military rounds. Mind you, that wasn't state of the art armour. But usually there are bounds by the armour guys, then by the bullet guys, then by the armour guys, etc.

And at under 30 feet, Dragonsbreath shells make an outright mess of even insert-loaded vests. The vest will effectively do you no good - the example I saw would have baked the vest, the wearer, and even badly damaged the insert plating. Of course, pretty high signature and not much 'general utility' but good for a close in raid if you really want to drop your target (and don't like your shotgun).

 

[mike wightman]

Thanks for the explanation, Corejob

Have you ever thought of writing any military supplements for Traveller?

 

[Todg]

Originally posted by kaladorn:
Since you seem to be in the know, could you clarify a couple of points:

1. What is the extent of expected blunt trauma?

Level IV vests typically have steel, or ceramic inserts. The interceptor has boron carbide ceramic plates.There is lttle or no backface trauma. There have been many reports of soldiers in Iraq being hit in the vest and not even knowing it at the time. Others stumble and then get back up. Level IV vests are hard body armor.

2. What is 'point blank range'? That is to say, has a bullet achieved its maximum velocity (I was led to believe not) before it has travelled some distance? Is point blank *actually* the highest threat?

Maximum velocity is typically at the muzzle. After that, the bullet is no longer being pushed by propellant gases and is decelerating. In a few rare case, maximum velocity is reached before the bullet reaches the muzzle. In the case of the .22 long rifle, maximum velocity is achieved after traveling about 14 inches in the barrel. After that, the drag on the bullet actually starts to slow it down.

Point blank range actually has different meaning. In the sense I used, I meant 'at the muzzle'. The other common use is the maximum range that can be achieved such that the bullet stays within the vital zone.

3. How do specialized munitions affect this? Bulk ammo is probably not the best armour piercing out there... aren't there specialized rounds that might still go through interceptor? Would the new 6.8mm likely change the balance?

NIJ Threat level IV vests must defaet a .30 cliber armor piercing round. The proposed 6.8mm round still has less energy than the 7.62x51mm. It won't be a better penetrator.

4. Where does Interceptor offer that level of protection? Head, front of chest, ??

Chest and back only. The rest of the vest is only level III. While a rifle bullet will penetrate the vest in areas not protected by the ceramic plates, the velocity of the round is still reduced and the severity of the wound is often lessened.

5. In areas not covered with that level of protection, how much lower is the protection and will these rounds be effective?

See above. Areas without the ceramic insert will stop pistol rounds and fragments. They will not stop ball rifle ammunition.

6. Lastly, what's the weight on a full Interceptor system?

16.4 pounds

I'm just curious. I've seen allegedly bulletproof vests shrug off hits from pistols and SMGs, but be diced by jacketed military rounds. Mind you, that wasn't state of the art armour. But usually there are bounds by the armour guys, then by the bullet guys, then by the armour guys, etc.

Most body armor is soft armor and will not stop rifle rounds. Only NIJ threat level IV or better can defeat full powered rifle rounds. This type of armor is heavy and bulky. It's use is usually restricted to high threat sitiations (like infantry combat or SWAT entries).

And at under 30 feet, Dragonsbreath shells make an outright mess of even insert-loaded vests. The vest will effectively do you no good - the example I saw would have baked the vest, the wearer, and even badly damaged the insert plating. Of course, pretty high signature and not much 'general utility' but good for a close in raid if you really want to drop your target (and don't like your shotgun).

Then effectiveness of DragonsBreath shotgun shells is highly overrated. It looks impressive, but DragonsBreath is nothing more than lighter flints loaded into a shotgun shell. You can start fires in dry areas or give someone a nasty burn. Maybe put their eye out. As a defense round, it is totally worthless. When we tested this round against a standard B21 sihouette mounted on a heavy cardboard backing at 10 meters, not a single 'pellet' penetrated the target # 6 birdshot was more effective.

For close in work, you are much better served by hardened buckshot or slugs. I personally prefer #4 buck for close in work (i.e. indoors). For a general purpose load, either high based 2 3/4" mag or 3" magnum 00 buck with 9 or 12 pellets respectively. For slugs, I like the BRI style saboted slug or the Silvestre style finned slug. The former will penetrate car bodies nicely, the latter is extremely accurate

 

[Uncle Bob]

Originally posted by kaladorn:
1. What is the extent of expected blunt trauma?

Virtually none. The impact on a SAP plate is spread over almost a square foot. Ignoring that, the 5.7x28 has about half the momentum of a 9x19mm pistol.

2. What is 'point blank range'? That is to say, has a bullet achieved its maximum velocity (I was led to believe not) before it has travelled some distance? Is point blank *actually* the highest threat?

Any bullet (not including rocket rounds like the Gyrojet) is at maximum velocity at the muzzle of the weapon. "Point blank" is commonly used to mean a very short range. Peneration of armor is highest at this distance, although some rifle bullets penetrate wood and sand deeper when the bullets slow down a little and are more stable.

3. How do specialized munitions affect this? Bulk ammo is probably not the best armour piercing out there... aren't there specialized rounds that might still go through interceptor?

Interceptpor vests with plates are rated to Level IV, which means it can stop M2 30-06 AP. It seems to stop all steel cored AP, slthough tunsten cored AP like the new M953 may defeat the vests at short range. New plates that can stop tungsten AP have been developed.

Would the new 6.8mm likely change the balance?

No. Right now there is no 6.8x43 AP. If there were, it would be less capable than the 30-06 or 7.62x51 AP.

4. Where does Interceptor offer that level of protection? Head, front of chest, ??
5. In areas not covered with that level of protection, how much lower is the protection and will these rounds be effective?

The intercepter vest covering the torso to the hips o/a is level IIIA protection, which will stop 44 Magnum and 9mm SMG at 450 m/s. The Level IV SAP plates are 25x30 cm and one is worn over the chest and one in back. These plates will stop nearly all rifle rounds.

The PASGT helmet is more protective than the vest without SAP plates. It has often deflected bullets from AKs (7.62x39mm), although it is not expected to do so.

6. Lastly, what's the weight on a full Interceptor system?

About 3 Kg vest, the SAP plates weigh 2.5 Kg ea, so 8 Kg total.

And at under 30 feet, Dragonsbreath shells make an outright mess of even insert-loaded vests. The vest will effectively do you no good - the example I saw would have baked the vest, the wearer, and even badly damaged the insert plating. Of course, pretty high signature and not much 'general utility' but good for a close in raid if you really want to drop your target (and don't like your shotgun).

I have some doubts here. A vest's shell is flammable nylon, but the kevlar armor in military vests nearly as fireproof as tbe nomex that race drivers wear. And the SAP plates are boron carbide, essentially very tough pottery like the lining of rocket nozzles. Dragons breath is spectacular but superficial, and if you miss your opponent's eyes he will make you pay. Buckshot is more reliable.
And yes, I have fired dragonsbreath. We expected a grassfire shooting in Texas in August, but we just stamped out a couple of smoldering twigs.