Are assault cannons AV or do you have to get AV rounds I can't find it in the book.

assault cannon are not AV weapons, no. you have to specifically purchase AV rounds.

Normal Assault Cannon ammo is not considered AV.

Edit: Too slow! That's what I get for re-wording my answer.

Only those (non-Naval) weapons with the (AV) tag in the Damage Code are AV by default. Anti-Vehicular Assault Cannon ammunition is found on pages 39-40 of the Cannon Companion.

To change it a bit APDS round, would that not be a cheaper option?

I don't know if English is your first language or you just mistyped, but that makes no sense. Please rephrase.

Agreed but as a cheaper option, I know what is trying to be said is that they are taking on heavly armoured vehicles. but I am looking at the price option... Not full out effectiveness, in that case go for a Launch weapon like a Dragon.

APDS has no different effect on vehicles than standard ammunition. It's not an affordable alternative; it's completely the same.

Since the weapon already has a Damage Code of 18D, APDS would only really be useful against enemy personnel with 13 or more points of personal armor, or for surprise attacks through heavy barriers. A moot point, since APDS ammunition for Assault Cannons does not exist in (canon) Shadowrun.

Like Arethusa said, APDS provides no advantage whatsoever over standard ammunition against vehicles.

Understood, I would have thought(along game Mechanics) That the slightly better penetration that normal as discribed in the SR3 Core. But under standandable that armour between 6 and 10 is going to pose a problem..

Not really. In real life, APDS will do things to light armored vehicles. In SR, nothing really makes much sense because most of the game was written with reality filtered through the writers' confused and addled view of the world.

I am looking at game Mechanics not real life saga's. I do understand that AV will be more effective

As was said, according to the game mechnics, APDS does no better than regular ammo against vehicle armor, no matter whether it is fired from an Assault Cannon or a Hold-Out Pistol.

And, again, there's actually no APDS ammo for Assault Cannons in the first place. Not in SR3/CC/R3 anyway.

OOPS... Yea I am getting confused between Miniguns, LMG MMG.

Yes, Assault Cannon (AKA recoiless Cannons with a difference.) They have there own ammo..

apologies

I believe that he was trying to convey knowledge of weapons technology, subtly, by mentioning in an offhand manner that assault cannons in Shadowrun bear some resemblance to recoilless rifles in real life. However, while the general premise is the same (projection of an artillery-type shell in a manner similar to a bullet from a rifle), recoilless rifles have a tendency to be tremendously large-bore (75mm, 57mm, etc...) while the assault cannon is, presumably, a much more tame 20mm.

Erm, most recoilless rifles (I won't count something like the recent HIWS that showed up at Blackwater) are what most people think of as bazookas. These are nothing like a large bore cannon like the described Panther Assault Cannon (and since we know where it came from, nothing like the same in Robocop). If you want a real life comparison, still nothing like a real life 25mm Barrett payload rifle.

I believe recoilless rifles are defined as different from bazookas (and LAWs, MAWs, RPGs, etc) by at least the fact that the former are loaded with a perforated/rupturing full artillery cartridge, allowing part of the propellant gases to be vented out of the breech and out the open rear of the weapon; the latter are simply loaded with a rocket (or similar projectile, without a cartridge), and all the propellant gas blows straight out the rear of the open tube.

AFAIK, the HIWS is not like this, because it simply has a moving breech/block/barrel system to reduce the recoil -- it doesn't actually vent propellant gases out of the weapon, does it? Also, I have a very hard time believing that any rifle-type weapon meant for long-range accuracy against point targets and often fired from the shoulder would operate in a manner at all similar to recoilless rifles.

That's not to say you cannot use some other manner of venting the propellant gases to reduce recoil, as proved by this anti-material rifle. Such systems are not likely to find much use and they certainly won't become a standard as long as other methods of recoil compensation allow weapons like the XM109 to be fired from the shoulder (though not perhaps very comfortably).

Why do they call the XM109 a four-round rifle if its features include two 5-round magazines?

~J

Typo? 5 is correct for magazine capacity, anyway.
Oft-linked PDF article on the XM109.

After the fourth round you have to replace the rifle.

4-rounds gives you a dead arm?

The 5th round is for justice?

No, the 2060s assault cannon is just a big, glorified antimatériel rifle, essentially incapable of touching a tank or anything else above light armor. The 2060s still have recoilless rifles, like RPGs and man portable guided missiles— but these are not assault cannons.

I remembered wrong, all weapons which eject propellant gases out the back of a more or less open tube system are called "recoilles rifle" in common use.

Like Arethusa said, recoilles rifles are still around in the 2060s in the form of LAWs, MAWs, ATGMs etc. Assault Cannons do not share the traditional roles of recoilless rifles: they are not anti-armor weapons, nor are they crew-served (although neither are most LAWs or MAWs). Combine that with ACs functioning on a different principle from recoilless rifles and you get that they are very different types of weapon systems indeed.