Hey Folks,

long time no see and right away a question for you: does anybody know how big an assault cannon or an gauss-cannon is, especially in comparison to a heavy machine gun? I have no books at hand at the moment, maybe it is written down somewhere?

Thanks.

From a fluff perspective, it uses light tank gun rounds - i would place it in this size category: http://en.wikipedia.org/wiki/Category:Anti-tank_rifles

The Assault Cannon that was featured in Robocop has always been the standard for what that thing looks like. They used a Barret M82 rifle with a prop imaging scope as the assault cannon in that movie. That said, I like the 20mm rifles that was suggested by NiL_FisK-Urd. They make much more sense, and could be fired from a rifle-like device not much bigger than the M82.

When asked this very question by newbie players, I reach out, I grab the nearest 12oz soda can, and I say "see this? This is the bullet an assault cannon fires. The bullet, not the case and propellant normally attached to it. Those are a bit bigger than another soda can. Starting to get the picture, now? "


Of course, in reality, a 20mm or 30mm Antimateriel Rifle is probably closer to what it'd actually be like. But for the purposes of a fairly cinematic RPG? Close enough.

I think the closest modern equivalent to SR assault canon is the Barrett XM109 "payload rifle" which fires 25mm explosive rounds. Oddly enough, it is actually shorter than a .50 M82 rifle (this review shows both side to side). I guess the 25mm round is so powerful that it does not need a barrel as long as a .50 rifle to be accurate. It's nonetheless slightly heavier, around 15kgs.

Imagine a minigun where you replaced the cylinder with one big hunking barrel, that's an assault cannon!
Now for a gauss rifle... Are you familiar with the Tau?

That thing is more of a mini-grenade launcher. Its not trying to do damage with kinetic force. Its about lobbing an explosive downrange.

I think pathfinder rail rifles are a bit smaller than the Ares Thunderstruck, which I'd say is a bit smaller than the rail cannons the broadsides carry.

Well bear in mind the Tau are quite short, a Tau rifle adapted to human size would be about right.

Assault cannons were described as firing explosive rounds in the previous editions. The 4th and 20th Anniversary editions only mentions "ammunition common to the primary weapon in many small tanks" (though Gun Heaven also mentions explosive rounds). As far as I know, the 25x59mm HEAT and canister flechette ammunition have yet to be developed, but they would fit the bill.

I'm with Nath on this one. ACs in SR fire explosive rounds. They are VERY loud dakka.

That thing doesn't resemble a Panther Cannon in the least.

20mm anti-tank rounds are exactly what theyre describing. They fly at ballistic speeds and hit with huge amounts of kinetic energy in addition to having explosive(or other) components.

That XM-109 does NOT do that. The projectiles are relatively slow.

Relatively. The M109 muzzle velocity is still above 400m/s. It's less than a sniper rifle (usually around 850m/s), and a lot less than an actual small tank gun (1,100m/s), and around the same speed than a pistol bullet.

They're not describing much actually: an assault cannon "fires shells equivalent to explosive bullets, but without the bullets inherent instability." "These highly stable explosive rounds are made of HDX superplast compound" (SR 3rd edition). It "fires stable superplast explosive warheads" (Cannon Companion), "special ammunition common to that used as the primary weapon in small tanks" "with tremendous recoil" (SR 4th edition), "large-caliber explosive rounds (Gun Heaven).

Past the "tremendous recoil", it never says anything on kinetic energy, and mostly focus and the explosive part. I see nothing inherently wrong as describing HEAT ammunitions as "common to that used as the primary weapon in small tanks," even if that ammo terminal velocity happens to be slower. Kinetic energy contributes little to zero to a HEAT effect. If the intent is to have a HEAT man-portable precision weapon, there's no point in increasing terminal velocity to the point that a man could no longer use it because of recoil (yes, I know, trolls have an easier time with assault cannons, but other metatypes can nonetheless use them). Obviously, we don't have the technology of SR. I just find it more likely to imagine that assault cannons are XM109 with some tweaks and possibly slightly faster ammo, than it is to imagine than they somehow managed to make a man-portable version of the M242 Bushmaster than can be fired with a mere bipod.

As was previously mentionned, I'd think they are lighter than heavy machinegun, on par with the anti-material riffles like today's Barret M-82 - think 30 lbs and five feet. A heavy machinegun is in the same length range but will weight from one and half to twice the wieght thanks to it's ability for autofire - and the heavy weight of a 100-round belt compared to a 5 to 10 round clip. When you're considering .50 and over ammo, it weights a lot.

Gauss riffle are probably about the same too - you save weight on the ammo (no propellant and casing) but add the energy storage and magnetic propulsion.

As far as assautl canon go, there's probably two main schools of design : either you use a relatively large bore, low velocity round which relies on a shaped charge to punch though armor and damage the target (probably somehting in the 25-30 mm range), or you go for a smaller and faster armor-piercing round which relies on kinetic energy to punch though and probably packs a small explosive or incendiary paylod to improve the damage behind the armor (probably in the 15-20mm range). The latter will be heavier, wih a stronger recoil but an increased range and accuracy.

From the in-book illustrations of the Panther XXL, I always pictured assault cannons as being around the size of a man-portable rocket launcher. All the rifles mentioned in this thread are about the right length, but not nearly bulky and hefty enough in my mind.

That said, I did stat up a homebrew custom Panther XXS, a working miniature assault cannon replica that serves as a heavy pistol with boosted AP, but which requires custom handmade ammunition and can only hold one round at a time. Had some quality laughs tossing that into a game.

~Umi

Ok, thank you very much. So the Assault Cannon or Gauss-Rifle wouldn´t be much bigger in the hands of a troll than a MMG or HMG? But now even more questions come up:

1) Do you think assault cannons and gauss-rifles are easily detachable?
2) How long would assembly take?
3) what skills do i need? I know that you need the armorer skill to re-adjust sniper-rifles, but simple breakdown for cleaning? Armorer skill? Come-on.
4) my GM says, that the gauss-rifle halves armor and then has an additional AP. Is that correct? Where is that mentioned? Didn´t find this section in the SR4A-book yesterday.

Thank you in advance.

4) Well, it's not mentioned in the SR4a book as I don't believe there are any Gauss weapons in it at all. The Arsenal Errata v1.3.2 that is, as far as I know, floating around the internet, states this for the Ares Thunderstruck (should be easy enough to find via Google). The entry for the S-K Taurus Light Gauss Cannon (Arsenal, page 124) also states this in the text. Can't think of any other Gauss weapons at this time, but I'd expect they all have the 'half armor' modifier.

Ah, this explains everything. The english errata are already included in german publishings. Thank you. Now we come to question 1-3. ^^

1: Do you mean, disassembled ...? Strictly RAW, none of them are. You can however get the "Easy Breakdown" modification, using the rules for Weapon Modification found in Arsenal

2: If you have Easy Breakdown? 3 rounds for Manual breakdown, or 2 rounds for Powered Assist breakdown. If you don't? As long as your GM wants it to take, with a probable minimum of 4 complex actions, possible more.

3: If you have Easy Breakdown? No skill required; Tab A goes into Slot B and is held in place by Pin C, and you're done.

You won't find those details in the books, because they don't go into that much detail, heck they didn't even get the distinction between a detachable (box) magazine and a clip right.
I'd say, they work like anti-materiel rifles, so they can also be field stripped like those weapons. The cool thing about assault cannons and other weapons is that their sights cannot be disturbed by combat. That rule only applies to sniper rifles.
Since there is no RAW for misfires and other malfunctions, ask your GM what you would need. Unless the character is unskilled, I'd simply say take a simple action to ready the weapon again. If the shooter has no clue, I'd increase the time to a complex action and require a LOG+Armorer (1) test.

It's this big:

http://robocop.wikia.com/wiki/Cobra_assault_cannon

When in doubt, go to the source material.

I've always thought of them as at least a stripped down 20mm anti-aircraft or anti-tank gun and potentially upwards of a stripped down 40mm.

http://en.wikipedia.org/wiki/Lahti_L-39

Well the assault cannon in arsenal looks a lot like that.
But the panther XXL looks like a tube with a handle on it pretty much.

That is, unfortunately, an outdated source. That gun is a Barret M82 modified for the film and there's no reason to suspect that the Barret Model 121 in Arsenal is too much off in size. Assault Cannons must be larger and bulkier than that.

Outdated source? How? The assault cannon was put into SR so that players could use that really big gun from cyberpunk genre entertainment. The original inspiration.

It's a really big gun that goes boom in an old cyberpunk movie that's called an assault cannon. What could be more accurate for a gun in a cyberpunk roleplaying game. Players wanted to use the gun they saw on the screen that looked really cool.

They just changed the name from "Cobra" to "Panther".

For me, the Solothurn S-18 was what came immediately to mind on reading the topic.

Okay, I like the S-18. Starting to get into the proper territory of "OH MY GOD LOOK AT THE SIZE OF THAT THING!"

~Umi

A little big for Man-Portable, though.
And a bit outdated.

The original source is a Barret M82 with some bulk added. That's the problem. It's exactly on par with the Barret sniper rifle presented in Arsenal. That is what makes the source outdated and requires a bigger potentially man portable weapon.

Or to look at it another way. Technology changes over time. What may have been an assault cannon in 2050 is now just a sniper rifle.

Aren't assault cannons supposed to be used with bi-/tripods or mounted to a vehicle anyhow?

Indeed, but the weight listed for the Solothurn S-18 is outrageous for a Man-Portable weapon. For a team, not so much; for an individual, outrageous.
At worst, it should use a Bipod. No Tripods for a single user weapon.

Blah blah modern composite materials blah blah I got a gun the size of a Tau rail cannon blah blah technobabble

Not sure where that came from, but okay. My point is that there are more modern weapons that fulfill the same roll as the Solothurn S-18 that are far less bulky and heavy, due to modern materials. *shrug*

The Denel-Mecham NTW 20mm Anti-Material Rifle for one. It weighs 57 pounds. *shrug*

Oh, no tone intended
My point is that people think to much realism and just need to embrace the dakka of a BFG.
Realism is kinda moot when you got a portable gauss rifle

I just like the S-18 purely for the sheer size factor. When I think SR Assault Cannon, I think "barely" man-portable, rather more likely troll-portable. I think something just shy of needing to be bolted to a vehicle to even think about firing.

The books say that assault cannons fire rounds that are usually found in the main guns of light tanks. If the gun doesn't look like some enterprising troll ripped it off a tank and stripped it down slightly to use as a source of More Dakka ™, I don't think it should be called an assault cannon.

~Umi

Well, You will never have a man (or troll) fireable 105mm+ Rifle. Sorry, not going to happen. Carrying something of that size is just not possible, let alone carrying any rounds for it.

But a 20-25mm Rifle will be useable. And there are current examples IRL today. The Denel-Mecham NTW 20mm Anti-Material Rifle I mentioned earlier is a good example of such a weapon.

We're also never going to have Dragons serving as US Presidents. An oversized assault rifle in 2070 works because of high tech materials, clever recoil compensators, and the like.

Now, no, it doesn't have to be 105mm+. That's fragging artillery, man.

But, say, a 75mm round? The kind fired by the main gun of the WWII era M24 Chaffee Light Tank? I can totally see a troll carrying a modern version of this.

~Umi

When Robocop got out in 1987, the Barrett 82 was a crazy thing that nobody used (though some snipers were already using .50 Browning M2 machine gun modified for single shot during the Korea and Vietnam wars). Except maybe for some special units who don't disclose their shopping list, the militaries didn't start buying and fielding the thing before 1990. I don't rule out that the person who introduced the Barret 121 in Fields of Fire in 1994 (Tom Dowd ?) did not realize that the rifle he was modeling it after already was the inspiration for the Robocop rifle who was itself the inspiration for SR assault cannon. In this regards, the fact the 25mm Barrett M109 looks a lot like the 12.7mm M82 may be an attempt at retconing the whole thing

On the other hand, I've recently seen footage of Mexico police carrying Barrett .50 rifle without scope, to be used at "short" range against cars who don't stop at checking points. Calling it a "precision rifle" or "sniper rifle" in this context is not really adequate. I found their use to be strikingly similar to how runners often use assault cannons.

Except the gun you are describing is not a RIFLE, per se.

Inverse to the size of the ***** of the person carrying it.

Assault cannon?

Still think the notion of a portable gauss rifle is more farfetched then a 75mm ballistic cannon that kicks like a donkey if you try and fire it without bracing.

Hence I always see them as a semi-automatic version of the Bushmaster, or one the 30 mm aircraft cannons from WWII. BOOM, frag you

There you go...

Much larger than 25mm is possible.

The M-18 Recoilless Rifle is a 57mm weapon; the Pansarskott m/68 is a 74mm weapon. Or the AT4, for that matter - it's an 84mm weapon.

recoilles 75 on scooter

The main problem here is recoil - a 105mm shell weight 15 kg. Say it goes out at 500 m/s (which is fairly low as far as artillery goes). Conservation of momentum means the 500 kg of troll, armor and gun firing it gets a 15m/s impulse. Enough to send him to sprawl to the ground in a mess, and probably injuring him in the process.

Of course if you're usign a recoilles design that problem goes out - historically, they were man-portable up to 50 mm, a 105 coumd be handled by a jeep and a 75mm could fit on a scooter for transport (that thing). The main drawback is a heavy backblast which makes indoors use problematic at best and heavier ammuniiotn than a regular round (the powder charge must be increased to provide the recoil-countering backblast)

Much higher than 50mm. See my links above.

Indeed, but Recoiless is not the same as a Rifle, names notwithstanding. The gunner of a Recoiless weapon does not suffer any recoil, and the area behind him must be clear of friendly people lest they die or suffer serious injury.

Having fired both SMAW's and AT4's/LAAW's, you do not do so with impunity in an enclosed area, whereas a rifle you can.

Isn't there this new bazooka thingie, that makes it so you don't blow your brains out with the shockwave, when firing from an enclosed position?

Sorry for the cringe, weapon buffs
Edit: AT4-CS
Like a slight breeze from the sea, instead of having your brain goo smeared on the wall.

There's a few designs around - thy all work on similar lines : instead of venting the gazes out in the back to counter the recoil, they use it to push an internal piston that ejects a mass of plastic shreds or smilar materials (think confetti on steroîds). They lose speed very fast and are cold, which makes them far safer than the usual backblast, even if staying right behind the weapon is still a very bad idea. The main drawback is a heavier and more costly round. But it also makes the firing a bit less sobvious as you don't have the very visible backblast to add to the muzzle flash.