22 replies to this topic

[Zigeunerskat]

Hello fellow Mechwarriors,

I am asking you for a short clarification.

As the title says, why seem AC5 cannons so much more popular than AC2s?


As I can see it, the AC2s have over both the AC5 and UAC5:

- higher (average) DPS
- higher rate of fire
- more range
- faster projectile speed
- take up less slots
- weigh less


While AC5s only have:

- higher dmg per shot
- less heat generation

However the break between AC5 shots is not long enough to torso twist.


So what is it that makes the AC5 stand out? Is the heat that bad with AC2s? I admit I havent played a AC heavy Mech in a while, so what is it?


Thanks for any helpful answers in advance

[zudukai]

they pair better with PPC's, higher damage per shot means less time getting shot, drop and speed are both very predictable, long range still, e.t.c.

[Modo44]

Heat is a big issue when you are also packing PPCs for pinpoint damage. The projectile speed of the (U)AC5 is very similar to that of the PPC, creating the perfect weapon combo. The bigger weapons also allow a mech to put out damage quickly and twist/dodge/hide. AC2s require exposing your mech to enemy fire for quite long, which ends badly when facing more than one mech at a time.

[Thorqemada]

You can build High-Alpha Mechs (30+ Alpha damage) with them if you pair 2 or 3 AC5 with 2 PPC.
AC2s run very hot and demand a higher exposure time than AC5.
U/AC5 count almost like 2x AC5 if the luck is with you and they do not jam often - Gamblers take U/AC5s.

[PhoenixFire55]

PPC / ERPPC projectile speed is 1500m/s. Closest AC match is AC5 / UAC5 at 1300m/s. The less difference there is between projectile speeds the better the chances of hitting same location are.

[Hex Pallett]

Short answer: Because AC5 is the better all-rounded weapon.

Long answer:

1. Pinpoint damage. Any effective build involving AC5s would include at least a pair, meaning 10 damage on a single spot in an instant. While at the same time AC2 has much better DPS, to get the same amount of damage output you'll have to fire 3x2 shots, which immediately leads to the following two points.

2. Range. AC2 is extremely hard to use within 100m, mostly because its lack of pinpoint damage. Leading your shots against a moving target becomes incredibly hard, and it tends to scatter around different sections of the target. So, while the DPS is high, the actual effect is not as much as AC5.

3. Cooldown. The short cooldown timer means firing AC2 requires constantly facing your target, while AC5 gives you a bit time to twist around and spread damage. Also, have you tried to fire AC2s at a moving target while moving yourself? Lots of compensation going on, isn't it? The cooldown time of AC5, however, gives you just enough time to re calibrate your shots.

However I do prefer AC2s in some cases, especially in long-range builds. Like Battlemaster 1D, when I could throw three AC2s in the arms. Or Phoenix Thunderbolt, when I have enough backup weapons - three MLas - to knife fight (also I couldn't fit an AC10 in there). Also my Jager, where I could have AC2s AND AC5s.

[M4NTiC0R3X]

The first thing that comes to my mind about AC/2 is this...

when you hold that button down you're exposed for the time you're doing ' good damage '

when you hold that button down your heat will remain where it's at and continue to rise.

Edited by M4NTiC0R3X, 12 April 2014 - 04:09 AM.

[ImperialKnight]

OP is underestimating the importance of heat in this game. It's the single most important resource you have. And synergistic effects

You can infinitely fire triple AC5s for marginally lower DPS compared to AC2s and that is huge. Cause that means you can shoot other weapon systems which means MUCH higher DPS overall

Edited by knightsljx, 12 April 2014 - 04:13 AM.

[C E Dwyer]

add to whats been said allready

Damage falls away less on long range shots once over effective range

The most important of all high rate of fire means nothing to poptarts.

[PACoFist]

AC2s are great for suppressing enemies. You can shoot up to 2 kilometres. No other weapon can do that, so you are safe from return fire. They don´t do much damage at that range but most players will still run for cover. If you have good view on the opposing team, you can hold them down, while your close-range fighters advance.

But for destroying mechs, I think heavier ballistics are better. The only ballistics I found useless are Gauss, due to the awkward charge mechanic.

[Wildflame]

It's a combination of greater pinpoint damage, less disparity between the projectile speeds (and therefore reducing the probability of spreading damage across multiple enemy components), and low heat (meaning it can be boated with PPCs for MOAR PINPOINT DAMAGE).

AC2s are great sniping and fire suppression weapons. They do incredible damage over time, but have two major weaknesses. First, they are hot - you cannot use other weapon systems effectively while firing AC2s. Second, they do relatively low damage per hit, meaning that though you do lots of damage, the damage is likely to be spread over multiple components.

When running AC2 Jagers I tend to hunt for XL kills, but even so generally I strip the enemy 'Mech's CT armour before killing their ST - that is damage wasted, because it did not contribute to getting the kill. The optimal way to kill enemy Mechs is to drill through their weakest component that [a] you can hit and [b] will kill them upon destruction.

Technically this means headshots, but the hitboxes are so small they are generally not worth seeking, with the possible exception of a completely still enemy at distance, or one that has overheated.

In practice this means the ST of a 'Mech you believe to carry an XL, or the CT otherwise. Again, ideally this would be from the rear, but only light 'Mechs tend to be fast enough to get into a position to shoot rear torsos, and they do so. For heavier 'Mechs, the goal is to core out their opposite numbers in ST or CT as quickly as possible, and taking minimum damage in turn.

Thus there are two basic objectives in MWO's combat:
1. Destroy enemy ST or CT as fast as possible
2. Take minimum damage in return (in order to continue doing #1).

Boating AC2s does work fantastically for destroying enemy 'Mechs fast - I regularly run 5xAC2 Jager-DD, and it is hilarious to me (and sad to the opponent) when I can kill a Blackjack who pops over the ridge to shoot before he can retreat into cover. Time to kill - 5 seconds or less.

However, for as long as you are doing damage with AC2s, you are showing the enemy your own torsos - in breach of principle #2.

Compare with AC5/PPC combos. You can put ~30 points of damage into one ST in one shot, then take your time to line up another. Even better, between shots you can torso twist and force the AC2 boat (me) to waste ammo on your arms (unless you're unlucky enough to have STs that stick out, such as Jagers, Hunchies).

If you have jumpjets as well, you can put ~30 points of damage into my ST in one shot and expose yourself for about a second. I may be able to put 20 points of damage into you in the same time but I guarantee it'd be spread across at least two of your three torsos.

Who will win, assuming equal skills? The poptart.

Even in a 'Mech without JJs, you may expose yourself for two seconds from 600m to hit me with ~28.5 points of damage (PPC dropoff and all). I may be able to put 40 points on you in ideal circumstances (not likely, given you're moving), and they are likely again to be spread across your three torsos and possibly an arm or leg.

Who will win, assuming equal skills? The AC5/PPC boat.

It gets worse when there are multiple 'Mechs per side. The AC2 boat can pump out incredible damage for about six to eight seconds depending on the map. After that, they have to time their shots to allow for cooling. If I have to run'n'gun, I am much, much less effective than an AC5/PPC boat thanks to the AC5s producing almost no heat.

This being said, AC2s work fantastically in their role - fire support. Every 'Mech can and should think twice before crossing open ground in front of an AC2 'Mech because they will get shredded. And if I have a nice shiny Fatlas to hide behind, AC2 'Mechs make an unbelievable force multiplier.

But I speculate that those situations rarely arise in high level matches, because the players are too aware - too coordinated - to need to expose themselves to extended bouts of AC2 dakka.

While I'm on the subject, my advice to people who wish to use AC2s effectively:
1. Positioning is key - be where you can get extended shots on your enemy, and where they cannot easily engage you. I generally set up on a flank for this reason.
2. Move perpendicular to the enemy while engaging - this makes you a harder target to focus on a torso and compensates somewhat for your own 'Mech's lack of precision. I like to think of it like being a big ship moving 'broadside' to enemy ships to unleash the barrage!
3. Practice shooting while moving to get better at keeping shots on target. The upside to AC2s is that missing does not cost you much, because your next shot is only 0.52 seconds away. Dak dak!

Edited by Wildflame, 12 April 2014 - 06:38 AM.

[Not A Real RAbbi]

Not that I use any of these (AC2, AC5, UAC5, PPC, EERPPC) that often, but when I do, I'm generally in agreement with the other responses.

PPCs throw out a LOT of heat; more so the ER PPCs. Pair that with the ridiculous heat production (especially with 2 or more of them) of the AC2, and virtually any build is going to have problems keeping up fire for more than a couple seconds.

AC2 goes alright, I think, as the sole long-range system on a mech. Say, you pair up 2 AC2 with some MPL or LPL on a Jagermech. The ACs are long-range only, and the lasers for up close, then it might be beneficial over the larger ACs. Building a CTF-3D for range, mixing ER PPCs and ACs? Stick to the AC5s and/or UAC5s, and you can sustain fire on distant targets a bit longer before heat steps in to dampen the fun.

At least, this is as I've observed it. I may be way off though.

[Hexenhammer]

TL:DR

Synergy with the PPC

[Amsro]

PACoFist, on 12 April 2014 - 06:36 AM, said:

But for destroying mechs, I think heavier ballistics are better. The only ballistics I found useless are Gauss, due to the awkward charge mechanic.

I do not like/dislike the charge mechanic, but if you can figure it out the Gauss is actually the best all around weapon. Great Rage, Great Damage, No Heat.! I even use this weapon on my medium mechs.

[Zelumbras]

As the previous posters already stated, there are a few main features to consider when comparing the AC-2 and the AC-5: heat, effective damage over engagement time (aka 'effective dps') and opportunity.


Heat vs Damage vs Weight
I believe it is easiest explained with examples of building a mech around each of the weapon systems. In this example i will use the Cataphract CTF-4X since it can effecively use 4 of each respectively.

Step 1: The basic build
This build only contains armor, DHS, the absolute minimum of 1 ton of ammunition per AC and a weight/cooling efficient XL-255 engine.
CTF-4X (AC-2) basic 15.38 max dps, 10 tons free, 35 slots free, 29% cooling efficiency
CTF-4X (AC-5) basic 13.33 max dps, 2 tons free, 23 slots free, 82% cooling efficiency

At this point, the AC-2 version looks vastly superior, except for the fact that it overheats after just 11 seconds while the AC-5 version can fire for over 160 seconds straight - but with so much weight and slots free, you should be able to easily counter that, right?

Step 2: Heat vs tonnage
In a second approach we test what heat efficiency we can achieve for the AC-2 version and how much additional weight we can free up with Endo-Steel and/ or FF on the AC-5 one.
CTF-4X (AC-2) cool-run full tonnage, 10 extra DHS, 49% heat efficiency, 20 seconds to overheat
CTF-4X (AC-5) Endo-Steel 5.5 tons free, 9 slots free, 82% heat efficiency, 2:43 min to overheat

The AC-2 version still runs hot when firing all weapons while moving but the heat is managable now and you can sustain the dps for a longer time at the cost of still having very low ammo and no weight/heat left for backup lasers.
The AC-5 version, on the other hand, has now enough tonage left to fit in some backup lasers, additional ammo and armor and/or ams. Having a very high heat efficiency is not very efficient (pun intended) in engagements that usually last less than 40 seconds. A few medium lasers will allow you to use your heat to a better extent and also makes you less susceptible to running out of ammo.

Step 3: Rounding up the builds
We now drop 2-3 heatsinks or some armor to add more ammo for the AC-2 version and fill up the free weight on the AC-5 version to better balance out the builds.
CTF-4X (AC-2) extra ammo = -3 DHS + 3 tons of ammo. 8 damage Alpha-Strike, 15.38 max dps
CTF-4X (AC-5) extra ammo/ ML = +2 Medium Lasers + 3 tons of ammo + some leg/head armor. 30 damage Alpha-Strike, 15.83 max dps

The AC-2 version will run too hot for extended brawling so it better sticks to medium-long range firesupport. It also requires line of sight for an extended time to do its damage, exposing it to enemy sniper and LRM fire during that time.
The Ac-5 version can do the same with slightly lower dps at range but adds the ML for more close range punch. The higher Alpha damage makes it a lot easier to concentrate your damage on specific locations on enemy mechs.


DPS vs Opportunity vs eeDPS (effective engagement dps)
As mentioned above, it is more difficult to concentrate all hits from a fast firing weapon on a specific armor section on an enemy mech - even more so if both of you are moving and the window of opportunity (how long you can shoot it without drawing too much fire) is short.
There is also a difference between a weapon systems average and initial dps. This is simply due to the fact that you are starting with the weapon being ready to fire (in contrast to the gauss for example) so if you fire, the first slug will hit after a very short time of reaction speed + ping + bullet travel time. In other words: bigger ACs get a headstart.
Even though it has higher average dps, the AC-2 needs some time to catch up to the AC-5s higher initial damage. The shorter the engagement time, the more the bigger ACs shine over their smaller counterparts (part of why i think that at least the AC-10 and AC-20 should fire burst rounds of 2-5 shots).

[Void Angel]

In other words, the additional front-loaded damage of the AC/5 is 2.5 times higher than the AC/2, and even though the AC/2 has much higher dps per ton, it has only .52 additional dps per hardpoint. The /2 is also far hotter for its dps; in order to fire a single AC/2 heat-neutral, you would need a total of 20 effective heat sinks - compared to only seven EHS for the AC/5.

It's much the same situation as the AC/10 in tabletop; by the time you get around to accounting for ammo, the PPC can add enough heat sinks to achieve the same net heat as the AC/10 (unless you only take ten shots) without the need for ammo. Which you take is dependent on whether or not the PPC's minimum range is a more important limitation for you than the AC's need for ammo. With MWO: the choice is between extreme long range, or mroe efficient firepower.

Edited by Void Angel, 12 April 2014 - 09:00 AM.

[kesuga7]

easier to use with less heat

[Koniving]

Zigeunerskat, on 12 April 2014 - 03:20 AM, said:

So what is it that makes the AC5 stand out? Is the heat that bad with AC2s? I admit I havent played a AC heavy Mech in a while, so what is it?

Thanks for any helpful answers in advance

They pair better with PPCs and LB-10/x.
Less heat.

AC/2s suffer GHOST HEAT! <--the number 1 reason AC/2s lost popularity. AC/2s are punished by "heat scale" for firing more than 4 in a 0.5 second window. However, each time you fire 1 AC/2, that window resets. So you could fire 1 + 1 at 0.3 seconds apart... for this pattern.
0 (fire 1). 0.1. 0.2. 0.3 (fire the second.) 0.4, 0.52 (fire the first again) and it'll count as 3 AC/2s fired.
Then it counts as 4, as 5, as 6, as 7, as 8, as 9, as 10.. By then you're getting +50 extra heat (5 PPCs of heat)!!!!!

That's why.
Otherwise... before:




The change (after the patches they happened at and the reactions).

Spoiler

Titled "Ninja" because on the original ghost heat thing it was Not punished or listed... yet it was.


Worse, after PGI stated it was intentionally added but working incorrectly. This is what "working correctly."

[Mims]

ac2s are good for damage done, ac5s are good for getting kills. also you have to be exposed alot more often to get the same amount of damage. ac2s are a good sniper support weapon where you can be out in the open, ac5s are better for guerrilla fighting (firing then taking cover then firing again) <<< basically the only way to play MWO and be successfull.

[Buckminster]

For me, it's all about the heat. I've tried using them in pairs (or in triples), and it just seems that they run too damn hot. You get the first few volleys off fine, and then it's cooking time.

So when I've been looking for lots of dakka, I go pair of UACs or trip AC5s. I want something that I can chainfire constantly, and not overheat with a dozen or so DHS. The UACs have the downside of the jam potential, but they are also a lot lighter than triple AC5s.

If you look at the weapon stats on Smurfy's, they have an "EHS" stat - the number of heat sinks you need to keep the weapon heat neutral. For an AC5 (or UAC) it only requires 7. The EHS of an AC2 is 20. It is far and away the worst ballistic as far as heat is concerned.

Although they are supposedly tweaking the ROF of some of the ballistics in the next patch, which may effect the math some.