THE BEST WEAPON IN MECHWARRIOR 5 CLANS IS...

The weapon you like using the most :^)


OBJECTIVELY THE BEST WEAPON IS...
The ER Small Laser

This little bad boy outshadows just about every weapon in the game. Not only is it super light, but it has very little heat, is super small, and has amazing DPS.
If you want to stomp the campaign, you should be strapping ER S lasers to EVERYTHING, EVERYWHERE, ALL THE TIME. Every other weapon in the game plays second fiddle to it.
The only downside is that it can't hit targets >600 metres away, which isn't really too bad of downside. So far the only tactic I've seen AI mechs use is to charge in and try to fight pointblank anyway. It only means you may take some turret fire in the campaign.

For a non-exhaustive list of the weapons and their stats in MW5, see below:


Probably the most significant column is the one on the far-right, "DPS per t + ammo".
This is how much DPS you can expect per tonne of weight after accounting for 1t of ammo.
Here you can see the ER S laser has nearly DOUBLE the DPS per t compared to the next best weapon, the SRM6.

Secondmost significant (if you're planning to use missles and ballistics) is the "Minutes to deplete 1t".
This is how long you can shoot before using up 1 tonne of ammo.
As a rule of thumb, I generally aim to have 8 minutes worth of ammo per weapon. So for ballistics I will bring about 2-3t of ammo per cannon.

In order of best to worst, the three weapon types in MW5C are:

Energy > Missiles > Ballistics

Objectively the best weapon type in the game.
Energy weapons are the main course, the favoured meal for our smorgasboard of destruction. It's very clear that these are the intended weapon set of the developers, and easy way to flex your superiority over the other mechs.

PROS
-Very low weight (6t to mount the HEAVIEST energy weapon vs 5.5t for the LIGHTEST ballistic)
-Uses very little slots (meaning you can fit any size energy weapon on virtually every mech)
-Can be dual-mounted and stacked very easily
-Infinite ammo (cooling comes free on every mech!)
-Hitscan with 100% accuracy (so you can focus down parts more easily, also great for the AI mechs)
-Fantastic DPS to weight ratio
-Every mech has plenty of energy slots
-Very long range
-Can shoot infinitely without cooldown if the mech is standing in water

CONS
-Limited by the cooling capacity of the mech

Missiles are the appetiser before the main course and should be treated as such. They're generally ok, but they'll run out of ammo very quickly.
Generally they should be used on full health targets in order to soften them up so you can focus them down.

PROS
-Less aiming required
-Ok DPS to weight ratio
-Ammo is interchangeable between different sizes
-Can be fitted on a lot of mechs
-Accuracy can be enhanced with Artemis + Tag + NARC

CONS
-Spreads the damage widely across the target mech
-Extremely ammo hungry
-Can be shot down by AMS
-AI loves to waste ammo
-Negatively affected by ECM

Objectively the worst weapon type in the game.
Ballistics truly are the dessert to our diabolical dinner of doom. They are what you mount AFTER you've added everything else, IF there's any room left. Their DPS is terrible, their weight is horrible, their slot requirements are massive, BUT they do make some pretty cool sounds.

PROS
-Great burst DPS potential with Ultra cannons (if you get lucky)
-Ammo has more damage potential per tonne than missiles
-Awesome audio & makes cool explosions

CONS
-Extreme weight requirements (5.5t MINIMUM to mount the SMALLEST cannon)
-Extreme slot requirements
-Projectiles have travel time
-Accuracy and range get worse with size
-Moderately ammo hungry
-Terrible DPS to weight ratio
-Terrible DPS in general (since it's extremely difficult to mount multiple cannons)

The ONLY saving grace for ballistics is the UAC/20 SLD. That thing is a BEAST.
If you don't know, you can crank the ROF of ultra autocannons by spam clicking. Every time you skip the weapon's normal cooldown though, you have a chance to jam the gun for 8-10 seconds. So if you bring the biggest possible round, then you're doing way less dice rolls per damage.
The UAC/20 SLD also brings DOUBLE the amount of ammo compared to any other 20 size ballistic cannon. It can literally drop mechs in 4 seconds. I suggest you try it out IF you have 15t to spare.

To paint the picture on just how terrible ballistics are, let's compare the humble AC-X 20 SLD to 4 ER S Lasers.

AC-X 20 SLD
12t weight (have to bring an extra 3t to have enough ammo for an entire mission)
9 slots used
20 damage
15.62 rpm
5.21 dps
5 heat
360m max range
500m/s travel time (so you need to lead your shots)

4x ER S lasers
2t weight (no extra weight wasted on ammo)
4 slots used
20 damage
19.05 rpm
6.36 dps
7 heat
600m max range
instant travel time

So despite being five times lighter, you actually get MORE dps with ER S lasers...

So with all that in mind, the optimal mech loadout looks something like this:

-Fill as many slots as possible with ER S lasers
-Then add at least 0.25t of armour on every component (on lighter mechs, 1t of arrmour effectively doubles the HP of that component which is VERY USEFUL)
-If you still have spare weight, consider bumping that armour up to 1t per component
-If you're finding you never overheat in missions or are being consistently out-ranged, upgrade your ER S lasers to mediums. ER M lasers can out-range just about everything.
-If there's still spare weight and you've filled out all the energy slots, consider adding missiles. You could get away with just adding more armour though.

And that's it.

Literally the most optimised mech is just maxing the small ER's, i.e building a Nova with x12 small ER lasers. Using this I've steamrolled the campaign on Expert.

All the other components don't really matter and are just nice to haves. For instance:
AMS will only stop a few missiles from hitting you.
ECM reduces enemy accuracy, but you need to be within 220m for it to work.
Targeting computers give +4% energy range and +5% projectile speed per tonne, big whoop.

Depending on your loadout, your tactics will need to change. Here's a few tips & tricks I've found.

If you're running mechs with a billion ER S lasers and armour plating, you can pretty confidently ignore everything below. Just tell your squad to follow you, then face tank everything. I'm pretty sure this is how 90% of players play the game anyway...

The mech AI is pretty rough. While your squad mates will kill enemies, they won't be terribly efficient about it. If left to their own devices, you will out DPS your entire squad.

If you tell the squad AI to attack a target, that squadmate will move into range of it's lowest range weapon before running in circles. So if your squadmate has a flamer on their mech, they WILL run to the enemy to fight point blank (looking at you, Adder...)

However, if you tell your squad to attack a target, and then issue a command to guard a position or reform on you, they WILL keep shooting that target AND stand where you want them to. This is essential if you're running a low DPS meme build (i.e ballistics only).

In the battle-map, you can actually queue your allies to attack targets by shift clicking enemies.

Your squad mates will tend to target components FIRST and the main mech body LAST, unless you damage the main mech body FIRST. I think they typically go for the weakest component always.

Short Range Builds
What I found helps for short range builds is constantly telling my squad to focus my target. By combining fire, you can drop enemy mechs a lot quicker.
Another great benefit is if there are ally mechs on the map. Let them go in first and tank all the damage for you :^)
Since you're so close, having an ECM can be beneficial.

Medium Range Builds
If you're running a lot of medium range weapons, then congratulations because you've actually got more range than 90% of the enemy mechs. They really are running ancient weapons with pathetic range.
A strategy I like to employ here is slowly retreating during an engagement to keep outside of the enemies range.

Long Range Builds
The trade off for the best range is having the worst DPS... When running long range builds, I generally try to stick to the high ground / vantage points wherever possible, place my squad's mechs in line formation, and continually back out whenever the enemy gets close.
One benefit is that you don't need to bring nearly as much armour. This is the one situation where an AMS is handy, as they'll only hit you with missiles.

Anyway that's about the jist of what I've found in MW5C. Any feedback is welcome in the comments.

If you think running billions of ER S lasers is boring, then I challenge you to NOT use any ER S lasers at all.