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Hey guys I'm half way done with building my first storm raven, I've given it a TL MM but I'm stuck on which weapon to choose. I want to go Assault cannon simply due to it being the most versatile weapon where as lascannon is longer ranged and will help it be better at shooting down other fliers and vehicles.

both work pretty well. can we get some info on the rest of your army? that might help weight it one way or another

Strictly speaking, 4 Assault Cannon shots have abetter chance at taking a hull point than a Lascannon shot.

Always the Assault Cannon my friend. 4 shots Str 6, Rending are the way to go, statistically anyways.

Assault cannon is statistically either on par (against a few things) or better (against most things) than the lascannon. The only thing the lascannon has over the assault cannon is range. Which is hardly ever a factor on flyers.

I'll throw my hat in with assault cannons as well.

In my opinion, glancing vehicles to death rather than exploding them has become more crucial than ever since 7th edition.

Magnets ....

I'd pick Assault Cannons. Can still threaten vehicles, but are more versatile. So if you bring ACs, you'll always be able to get some good use out of them.

Keep in mind that the Stormraven has Power of the Machine Spirit. So that TL MM can fire at a completely different target from the Assault Cannon if you wish.

I like the TLLC to get another high strength low AP shot.

 ruminator wrote:
Magnets ....

This.

Concur on the magnets, but I'll also say that I don't think I've ever found a good reason to use anything but the assault cannon.

I found when assembling mine that the turret weapon can be dry fitted on so it leaves all weapon options open if you don't want to fork out for magnets

You should definitely magnetize. The magnetization keeps you from loosing the weapons from minor bumps.

Assault cannons are somewhat more versatile (though with all the vehicles and MC this may not be absolutely true). Both are definitely worthwhile though.

Keep in mind that assault cannons cannot explode vehicles anymore (unless open topped) and only ignore 2+ and 3+ armour saves 1/6 the time versus the Lascannon's 100% of shots.

The turret nature of the weapon can also be made use of for the range. I have on many occasions flown my stormraven on point blank to a helturkey's face and at a almost perpendicular angle to the side armour of a tank. The MM and missiles shoot the flyer and the lascannon PotMS and goes after the side armour of the tank. This is much more likely to happen with a 48" range weapon than a 24" range weapon.

The assault cannons are however better against AV10 and 11 and against most infantry. Multiple shots also help when you need to jink.

Twin Linked Plasma Cannon!

You've got a 56% chance of landing a hit on the scatter dice.

 DanielBeaver wrote:
Twin Linked Plasma Cannon!

You've got a 56% chance of landing a hit on the scatter dice.

And can't shoot other flyers. IMHO the primary role of the SM birds is keeping the sky clear. Ground attack, while useful and important, is secondary.

In 5th, the answer was easy. The assault cannons were vastly superior. In 6th with AP2 getting a +1 on the table, I'd call it a push. In 7th, where AP4 weapons can't ever explode vehicles that aren't open-topped, I'd take the lascannon.

I ran mine with Assault Cannon, MM and Hurricane Bolters for both anti-flyer and the ability to BRRRRRT if I needed to.

I did the maths on this in sixth, infuriatingly I cannot find it and so will have to tap the whole damn thing out again on my phone. I am doing this to see the differences 7th has made since the AC can no longer explode. My hypothesis is that the AC is still vastly superior but until I have done the maths on every target I am as in the dark as everyone else. If I type all this and find dakka has a character limit, I will be depressed for the rest of summer...

First of all, to save time I will write a key:
H = chance to hit with one shot = 2/3 + 1/3*2/3 = 8/9.
Hps = average hps taken off (either through glancing or penning)
Ors = chance of eliminating in one round of shooting. (For the assault cannon I will have to work out the inverse and take it away from one, this is by far the most laborious part but I have my trusty tree diagram with 16 outcomes at hand to assist). Multiply this by 100 to get % chance.
L = twinlinked lascannon
A = twinlinked assault cannon
W = winner

I am not taking into account damage caused by penetrating hits unless it is an explodes result as I may just go insane otherwise.
I may make reference to cover saves where appropriate. But the conclusion will be based upon targets being in the open. Screw holofields. Neither will invulnerable saves be taken into account. Although as the mathmatically gifted amongst you will realise neither type of save will effect the result as it effects both weapons to the same extent.
Invisibility doesn't exist. Apart from that, neither should ever have to snap shot as they are both mounted on a flyer.
Other things that don't exist in my little world for the moment are psybolts for the assault cannon and enthropic strike - if you want to go lower than av10 feel free to do it yourself :-p.
Also everybody in the following version of 40k wears power armour - even orks, so for the moment there os no such thing as opentopped!
I shall round to 4dp everytime.

So here we go:
Vehicles:

AV14 4hps (I like FW but I think it is obvious that the Las wins with Ors against 5hp vehicles such as the spartan)
Hps
L) H x 1/3 = 0.2963
A) H x 1/6 x 2/3 x 4 = 0.3950
W = A

Ors
L) H x 1/6 x 1/6 = 0.0247
A) (H x 1/6 x 2/3)^4 = 0.0001 (shoulda done this to sig fig)
W = L

AV14 3hps
Hps
As above
W = A

Ors
L) 0.0247
A) 1 - ((0.0987654321*)^2 x (0.901234567**)^2 x6***) + ((0.0987654321) x (0.901234567)^3 x4) + (0.901234567)^4) = 0.0036
W = L
*chance of hp stripped
** chance of hp not stripped
*** Number of outcomes with this chance

Av13 3hps
Hps
L) H x 1/2 = 0.4444
A) H x 1/6 x4 = 0.5926
W = A

Ors
L) H x 1/3 x 1/6 = 0.0494
A) 1 - ((0.1481481)^2 x (0.8518518)^2 x6) + ((0.1481481) x (0.8518518)^3 x4) + (08518518)^4) = 0.0116
W = L

Av12 3hps
Hps
L) H x 2/3 = 0.5926
A) H x 1/6 x 4 = 0.5926
W = Draw

Ors
L) H x 1/2 x 1/6 = 0.0741
A) Same as Av13 3hps
W = L

Av11 3hps
Hps
L) H x 5/6 = 0.7407
A) H x 1/3 x 4 = 1.1852
W = A

Ors
L) H x 2/3 x 1/6 = 0.0988
A) 1 - ((0.296296296)^2 x (0.703703703)^2 x6) + ((0.296296296) x (0.703703703)^3 x 4) + (0.703703703)^4) = 0.080927
W = L

Av11 2hps
Hps
As above AV11 3hps
W = A

Ors
L) As above = 0.0988
A) 1 - ((0.296296296) x (0.703703730)^3 x 4) + (0.703703703)^4)) = 0.3418
W = A

Av10 3hps
Hps
L) H x 1 = 0.8889
A) H x 1/2 × 4 = 1.7778
W = A

Ors
L) H x 5/6 x 1/6 = 0.1235
A) 1 - ((0.444444444)^2 x (0.555555556)^2 x6) + ((0.444444444) x (0.555555556)^3 x4) + (0.555555556)^4)) = 0.2341
W = A

Av10 2hps
Hps
As above Av10 3hps
W = A

Ors
L) Same as the above Av10 3hps
A) 1 - ((0.444444444) x (0.555555556)^3 x 4) + (0.55555556)^4) = 0.5999
W = A

Waveserpent with shield up, no jink, no holofields, no cover (AV12, 2+ save against pens)
We have already seen that hps is a draw.
Ors
L) H x 1/2 x 1/6 x 1x6 = 0.0123
A) 0.0116 (same as av12/13)
W = L


So out of 18 catagories, there are 2 draws and the Assault Cannon wins 10 out of the remaining 16.
There are other advantages for the lascannon penning such as higher likelyhood to cause lasting damage even if it doesn't explode its target.
Against AV12 is the only catagory that the Lascannon wins hands down, unless taking into account serpent shield which brings it very close.
Against av13 it will take more than 20 bs4 twinlinked lascannon shots to cause an explode result on average. You are going to have glanced it out by that point. So relying on small percentages for an explode result is playing it risky imo.
If you like playing the one-shot game, the lascannon definitely works better in 7th against the higher end targets. However, if you like to rely on the more reliable (thats not my opinion - that's maths) glancing a tank to death, the assault cannon is better against every single armour value barring one (and against that one it draws). The small percentage chance of explodes begins to get even smaller when you take into account cover, jink and invuln saves.
Whilst 7th has brought the weapons closer together than they were previously, 7th has also made glancing even more of an attractive option. Whilst a single shot of a lascannon has halved its potential of an explodes result, other weapons have utterly lost that ability against anything other than open topped vehicles. As 7th progresses, I predict you will see even more guns on the battlefield with the objective of glancing out tanks. Therefore we must take into consideration that the armament of a raven (barring the mm maybe) is there to assist other guns at glancing out tanks with teamwork being the key. Which gun is better suited for that task: the assault cannon.

I have to go out soon but will do the same for infantry and MCs later.

It really depends on what you need it to do.
I want to cripple or kill enemy flyers, so I run lascannons.
They have a slightly high chance of getting a useful pen hit, and I find double the range invaluable.

I accept that I'm less likely to kill enemy flyers, and I'm fine with just maiming them.

Magnetize

Though it depends which army version you're building

GK- Assault cannon without a doubt, psybolt ammo makes it str 7

Any other faction type is a toss up

Assault Cannon