The Inner Sphere has a wide variety of armor types, with a good number of specialty variants. But, as I’ve said in previous articles, your choice in armor is one of your least impactful ways to save on tonnage. Still, it is one of the choices you make in ‘Mech design and it is worth knowing how each of these armors compares to each other.

NOTE: All armor point calculations round down. If your design would have 17.92 points of armor? It has 17 points.

The main big choice for armor is going up to Ferro-Fibrous from standard armor. This gives you an extra 1.92 armor points per ton, or a 12% increase from standard armor (increasing from 16 to 17.92 points per ton). The down side is it takes up 14 crit slots, and even in a best-case your ‘Mech won’t have more than 57 slots to work with. Dedicating 1/4th or more of your crit slots to armor is no small investment. But, compared to the weight savings of Endo Steel, the pay-off for Ferro-Fibrous is small.

If you want 304 points of armor on your Atlas, it costs you 19 tons of standard armor or 17 tons of Ferro-Fibrous. 14 slots saves you 2 tons, compared to Endo Steel saving you 5 tons for those same 14 slots. The difference is that armor types like Ferro-Fibrous can give you some partial benefits in between half-ton savings. For example, 2 tons of Ferro-Fibrous gives you 3 more points of armor than 2 tons of Standard. Still, probably not worth losing 14 slots, but if you have nothing else to spend the space on it can be worth it!

Ultimately, what this does for Ferro-Fibrous and its variants is it biases in favor of heavier mechs receiving greater savings. The other problem with these types of armor is that you shouldn’t ever build a ‘Mech with Ferro-Fibrous in mind: it should always be the last decision you make. After you’ve accounted for your Engine, your Internal Structure, your Heat Sinks, and your weapons payload check if you have 14 crit slots to spare. If you do, use Ferro-Fibrous Armor. It won’t be until you get to ‘Mechs of 45 tons and up that it can save you a full ton or more of weight.

Heavy Ferro-Fibrous does everything that Ferro-Fibrous does but bigger and faster. It gets you an extra 3.84 point of armor per ton, a 24% increase compared to Standard armor. Most impressively this is more armor per ton than even Clan Ferro-Fibrous (19.20/ton for Clan FF compared to 19.84 for Heavy FF). Of course, there’s the cost: 21 crit slots.

From our example of armoring an Atlas before, where it’d take 19 tons to get 304 points of armor Heavy Ferro does 307 points in 15.5 tons. So at the upper end of this, you’re saving 3.5 tons on armor (still lower than the 5 tons Endo Steel could save you). What’s nice about Heavy Ferro-Fibrous is that you can see your weight savings much faster, as a 25 ton ‘Mech that wants the max of 89 points needs 5.5 standard to reach that but only 4.5 Heavy Ferro. The real problem is it costs about 40% of your available crit slots to mount it. Once again, not something you plan a ‘Mech around but something you luck into at the end of the design.

That said, the weight savings on Heavy Ferro-Fibrous can be substantial enough that it lets you trade a Standard Gyro for a Compact Gyro, gaining you survivability and extra crit slots. So remember that if you have 19 slots free. Regular Ferro-Fibrous can do this as well, but it’ll come up much less often.

Lastly, we have Light Ferro-Fibrous. It almost gets you an extra point of armor per ton, but not quite. Light Ferro gives you 16.96 points per ton, which means you don’t even see a benefit until you’ve used 1.5 tons or more of armor. It can’t even save you a half a ton until you get into ‘Mechs of 144 tons and up, and its best-case is a savings of 1 ton buy purchasing 305 points of armor for 18 tons instead of 304 points for 19. On paper, it’s barely relevant.

That said, I love Light Ferro-Fibrous. Because it only takes up 7 crit slots, you can add it to almost anything. Unfortunately, because the benefits are so modest you’re often only getting a few extra points of armor as a bonus rather than any weight savings. This makes it more of a luxury item than anything else.

Some of my favorite armor types specialize in defense against specific damage types, and the ones that most appeal to me for ‘Mech design are Laser Reflective, Reactive, and Ballistic Reinforced. Each dramatically improve their defenses against a particular type of attack (energy, missile, and ballistic/missile respectively). Unlike the Ferro-Fibrous category of armors, these are very important and mission-specific. If you want to build a ‘Mech using these, you should make that decision at the start and not at the end of your design.

Laser-Reflective armor grants the same number of armor points as Standard armor, but costs 10 crit slots. In exchange, those crit slots grant a bonus against energy weapons and a penalty against physical damage (falls, melee attacks, collisions, and artillery or area of effect weapons). Honestly, the frequency of energy weapons makes this trade-off excellent from the start.

Laser-Reflective armor reduces damage and heat from energy weapons by half, rounded down to a minimum of 1. In exchange, it takes double damage from area of effect weapons, falls, physical attacks, and moving through building walls. It has an additional negative effect of a +2 modifier on their armor-piercing effects rolls of things like Tandem-Charge or AP ammo for autocannons. Honestly, not something that comes up all that often in my thinking.

So Laser-Reflective armor is best used on ‘Mechs that are very likely to suffer damage from energy weapons and very unlikely to experience physical damage. That most often means scout ‘Mechs who are fast enough to avoid all but pulse weapons or ‘Mechs that operate largely underwater (a rarity, but worth mentioning because I love underwater combat). These aren’t the only situations, and you may well find other use cases. I built a 60-ton brawler intended to 1v1 Clan ‘Mechs of similar role and tonnage, and it also relies heavily on Laser-Reflective armor for its endurance.

Reactive armor once again provides the same number of points of armor per ton as Standard, but this time uses up 14 critical slots. In exchange, it takes all damage from explosives (missiles, mortars and artillery) and cuts it in half (as before, rounded down to a minimum of 1 point per grouping). As an added bonus, it does ignore any special abilities of armor-piercing effects from specialist weapons like AP ammo or Tandem-Charge SRMs. It does have a small risk of exploding on a critical hit (1 in 36) and discarding all remaining armor in that area and applying 1 point of damage to the Internal Structure.

That this means is Reactive Armor is especially good on any ‘Mech that’s expected to face a lot of damage from missile weapons, and the most damaging missile weapons are SRMs. That being the case, I really like it on ‘Mechs that do a lot of short-range brawling. That said, I typically prefer ECM and AMS systems as counters to missile weapons because they take up fewer critical slots. Although, if you’re going to be in a missile-heavy environment (like underwater combat where your opponents can only use reduced range energy weapons or torpedoes) it can be an excellent choice.

Ballistic-Reinforced is the first armor in this category that offers fewer points per ton of armor than Standard at 12 instead of 16. And that’s a pretty significant drop in protection, but at the same time it provides a dramatic benefit. This armor type halves damage (rounded down, minimum of 1 again) from all ballistic and missile weapons with no down sides when compared to other damage types. It does take up 10 crit slots to do this, but halving damage against everything from SRMs to Gauss Rifles is really something.

Except when would you want to use this? By the time the tech is available, everyone has access to double heat sinks and energy weapons are plentiful. Your best use-case is against someone who still believes in autocannons… so… invading the FedSuns? Given that it was invented by the Draconis Combine, that does make sense. But gameplay wise, I’ve struggled to see use cases for this. My best idea was as specialist armor on a Sniper ‘Mech so that it can better resist counter-sniping from LRMs and Gauss Rifles. Combined with a Blue Shield Particle Field to handle PPCs, and you might have something there.

I admit, this one’s a mystery to me! Leave a comment if you have a great use-case for it.

This category gives me the chance to talk about a pair of armors that don’t really fall into other categories. Hardened Armor trades top speed and ease of movement for the potential for greater protection. Stealth Armor is a way to trade crit slots for turning an ECM system into a TMM modifier.

Hardened Armor comes up-front with some unpleasant side effects: it inflicts a +1 increase to the difficulty of all PSRs and it lowers run speed by 1. That’s huge, since falling down is very risky and losing potential TMM in exchange for armor isn’t often a great trade-off. So what does it get you? Instead of buying 16 points per ton, it buys 8 points per ton… except not really. Every point of armor now takes 2 points of damage to remove. That means you need to take 40 damage in a phase to trigger a massive damage PSR instead of 20, and it means you can armor your cockpit enough to survive what would normally be a one-hit kill. As an added bonus, it ignores any armor piercing effects from weapons and applies a -2 modifier to any roll to confirm Through Armor Critical hits.

So when should you use Hardened Armor? To get the most out of it, you need to be armoring your ‘Mech to more than 50% of its maximum possible number of armor points. That’s the first point. Second, should it be on faster or slower ‘Mechs? I honestly think this is a bit of a wash. On especially slow ‘Mechs, you might miss out on a point of TMM. On faster ‘Mechs, you can afford to lose 1 point of running. For me, I feel the pain most on medium-speeds. I hate dropping from 4/6 to 4/5 than I do dropping from 6/9 to 6/8.

So what does this really mean? To me, it means Hardened Armor is good for very slow Assaults and reasonably fast Lights and Mediums. It also means you want to be putting at least 7pts of armor (14 points of protection) on the Head location so you can survive 15 point hits from PPCs or Gauss Rifles. Other than that? Go nuts!

Stealth Armor awards the same amount of armor per ton as Standard, but takes up 12 crit slots plus an ECM source. In exchange, it can blind your sensors and make it harder for everyone else to shoot you at the cost of 10 heat. While active, your Artemis and Active Probes are disabled, but enemies suffer a +1 to hit your ‘Mech at medium or +2 at long ranges. In addition, you cannot be the secondary target.

This is just a worse Null-Signature System. That said, you can get stealth armor in the 3060s whereas Null-Sig is LosTech until 3110. The 12 slots of investment is pretty hefty. In general, I would prefer using those 12 slots to save weight and spend that tonnage on a bigger engine. However, if you’re playing a scenario where you want to run with Hidden ‘Mech rules, Stealth Armor may be an option!

Modular Armor isn’t really armor. It’s equipment payload that can be used independently of your choice in armor. But it’s pretty neat! For 1 ton and 1 crit slot, you can add 10 points of armor to the location the module is installed. It then takes hits directed at that location before the ‘Mech’s normal armor would.

The real problem I ran into is “when do I want to use these?” By the time you have access to Modular Armor, you could just use Hardened Armor instead. So you really only want to use Modular Armor on ‘Mechs that can’t afford PSR penalties and need all of their run speed, but also have run out of other types of defenses. To me, that means Light ‘Mechs where tonnage is the tightest and these offer some of the least tonnage effective protection around.

From my point of view, Modular Armor is competing with ECM, AMS, Chaff Pods, Superchargers, MASC, and Active Probes. Now, most of those are anti-missile defenses. So if you need a light ‘Mech with lots of protection against energy and ballistics, you might consider spending tonnage you would normally reserve for ECM/AMS on these. I don’t think they’re bad, but I do think they’re a severely specialized tool.

These are armors that I just struggled to see a common use-case for. At best, maybe, they’re a good thing to use in some sort of narrative campaign play. But in standard play? I just didn’t know what to do with them.

Impact-Resistant is another specialist armor, but not impressive enough to include in the previous category . It’s the second specialist armor to provide fewer points per ton in defense than Standard armor, offering 14 points per ton instead of 16. On top of being inferior overall protection, it has extra vulnerability to hull breach checks and armor piercing weapons. What does it provide you in exchange? A reduction of 1pt of damage out of every 3pts of physical damage received. So you can charge other ‘Mechs or Kool Aid man through walls a little easier, I guess. But why? It’s never going to make up for the defenses it’s lost.

If you find yourself wishing you could reduce damage from physical attacks, don’t use Impact-Resistant Armor. Just install some Spikes. They weigh 0.5 tons and take up a single crit slot, defending the area they’re installed in by reducing physical attack damage by 4 points (to a minimum of 1). Additionally, they add 2 damage to your charge attacks.

Heat Dissipating armor grants 10 points of armor per ton of ammo, making it the worst one we’ve discussed so far. On top of providing less armor per ton than a Retro Tech ‘mech, it also costs 6 critical slots. For this cost, your ‘Mech reduces heat effects from external sources by half, rounded down. You know what else offers this benefit? Laser-Reflective armor.

Admittedly, Laser-Reflective doesn’t halve environmental sources. But do you really want to lose 37.5% of your armor in exchange for the ability to halve penalties from hot mud and extreme weather? I’d rather spend 1 to 2 tons on extra Heat Sinks than 1-2 tons of specialist armor to make up for the lost protection.

Did you like how Hardened Armor negated armor-piercing effects and resisted TACs? Did you want all of those benefits with none of the down-sides of Hardened Armor? Anti-Penetrative Ablation armor does that… except it’s also substantially worse than Standard armor. So… you could literally just use Standard armor and be better off.

At 12 points per ton and taking up 6 crit slots, Anti-Penetrative Ablation armor is one of the least impressive armor options around. Seriously, just take Hardened Armor, put AES in the legs, and mount a Supercharger. On light or medium ‘Mechs, that’ll cost you fewer crit slots that Anti-Penetrative Ablation armor and probably fewer tons in the long run when you consider how many extra tons of armor it’d cost you to bring your ‘Mech up to average.

You may think I’m kidding, but keep in mind our example of 19 tons of standard for 304 armor for your Atlas? 306 points of Anti-Penetrative Ablation armor costs 6.5 tons more than that (25.5 tons).

Armor selection was kind of a weird topic for me to tackle with these articles, because to me it’s either very situational (specialist armors) or a non-choice (Ferro-Fibrous & friends). That said, I did think it was worth writing about. So I hope this was helpful!