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Invulnerable Saves
Some models possess supernatural reflexes or force fields that grant them an invulnerable save, capable of evading or turning aside even the most powerful weapons. Each time a wound is allocated to a model with an invulnerable save, the Armor Penetration characteristic of that hit is reduced by 1 (to a minimum of 0). In addition, you can choose to use either the model's normal Save characteristic or its invulnerable save, but not both. If a model has more than one invulnerable save, it can only use one of them – choose which it will use. If you use a model’s invulnerable save, it is never modified by a weapon’s Armour Penetration value.

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8e seriously changed how Invulnerable Saves and Armour Saves work.

In previous editions, Armour Saves were binary. You had your full Armour Save, or you had no Armour Save. Therefore, Invulnerable Saves were an extremely useful backup that kicked in when you had no Armour Save. A Terminator always had a 2+ Armour Save... but even if your opponent went to the trouble of bypassing that save with an AP1 Meltagun or a Power Sword, your Terminator could still get a 5+ Invulnerable Save. Your Terminator was super tough against light arms fire, and still pretty tough against the most powerful weapons in the game! Against 120 wounds, your Terminator would save 100 vs AP5, 100 vs AP4, 100 vs AP3, and 40 vs AP2 (instead of 0, as would be normal).

In this edition, Armour Saves exist on a sliding scale, which means that your Terminator's 5+ Invulnerable Save isn't so much of an emergency backup as it is a lower threshold. This has the perverse effect of encouraging the use of middling-AP weapons against units with combined Armour/Invulnerable Saves. AP-1 weapons work normally against Terminators, reducing them to a 3+ Sv. AP-2 weapons work normally against Terminators, reducing them to a 4+ Sv. AP-3 weapons work normally against Terminators, reducing them to a 5+ Sv. It's only AP-4 weapons (or the very, very rare AP-5) that are in the least bit relevant to a Terminator's Invulnerable Save, and that's basically just Meltaguns, Lances, Heavy Plasma, and Chainfists. Everything else, from Power Fists to Plasma Guns, works just fine. The Crux Terminatus is useless against Autocannons, and gives you an extra pip of Sv against a Dark Lance. Against 120 wounds, your Terminator would save 100 vs AP-0, 80 vs AP-1, 60 vs AP-2, and 40 vs AP-3 or more.

This version massages that change by allowing Invulnerable Saves to interact with the non-binary nature of AP in 8e – they work normally, but also blunt the impact of "weak" weapons where your Invulnerable Save wouldn't have an effect but your Armour Save would still be reduced. What's the practical impact, here?

Daemons, Wyches, Priests, and other units with an Invulnerable Save that is equal to or greater than their Armour Save are completely unaffected, just as they were by the 8e change.

Terminators (2+/5+)used to treat AP-4+ weapons as AP-3. Now they treat AP-4+ weapons as AP-3, AP-3 as AP-2, AP-2 as AP-1, and AP-1 as AP-0. Same deal with Possessed (3+/5+) and other armoured+invulnerable units, except knock the cap down to AP-3+ being treated as AP-2.

Units with a 4+/5+ save – like Tau Fire Warriors with Shield Drones – may need tweaks (like being bumped down to a 6+ invulnerable, or selective invulnerable saves) to represent the new impact on AP-1 weapons. You can simplify the wording of abilities like the Tarsus Buckler to "this model has a 6+ invulnerable save against attacks with AP-1". All Is Dust becomes "you can re-roll saving throws of 1 for Rubric Marines if the attack has a Damage characteristic of 1."

I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

Ice_can wrote:
Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

No more effective than it was in earlier editions, though? I don't have a problem with Terminators getting a 2+ save against most weapons – my only issue is the way that 8e rewards weaker weapons instead of only blunting high-powered ones. In the scenario you describe, those Terminators have 2+ saves against AP-0 (fine), 2+ saves against AP-1 (fine), 2+ saves against AP-2 (fine), 3+ saves against AP-3 (fine), and 4+ saves against AP-4 (fine).

It doesn't make them more durable against AP-0 weapons, but nor did earlier editions – and I'm not seeking to address whether or not Terminators are good, just to resolve the weird situation whereby a Heavy Bolter, Krak Missile, and Plasma Gun all function normally against a Terminator... but Meltaguns and only Meltaguns run into a forcefield.

Ice_can wrote:
It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

Invulnerable saves aren't meant to be especially effective against light weaponry – they're meant to be universally effective against all weaponry, since your Wyches can backflip over a lascannon blast just as easily as a boltgun shell. It doesn't matter how strong the weapon is if it doesn't hit.

The only problem with this concept is that units with both armoured and invulnerable saves no longer flip between one or the other – they eat penalties on the former until they hit the latter. The problem isn't the invulnerable save itself – it's that units which used to be near-impregnable except to high-powered weapons are now more vulnerable, relatively speaking, to light armor-piercing guns. The problem is that light armor-piercing guns are totally untouched by your forcefield or holy aura or whatever, whereas in the past they were either affected (high enough AP to beat Armour) or couldn't affect you anyway (AP too low to beat Armour).

Ice_can wrote:
Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

At that point you might as well bump Invulnerable saves up a pip (i.e. 5+ becomes 6+) gamewide and let units take both in succession. 2+, reroll 1s, is +13%, and 2+ followed by 6+ is +16%. That's how Ward Saves used to work in WHFB – you roll Armour Saves, then Ward Saves. I don't recommend it, but it's certainly simpler.

Ice_can wrote:
I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

So my Daemons get, instead of a 5++, a 6+ rerolling 1s? Or, if the weapon has any AP at all, they just don't get a save?

RevlidRas wrote:

Ice_can wrote:
Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

No more effective than it was in earlier editions, though? I don't have a problem with Terminators getting a 2+ save against most weapons – my only issue is the way that 8e rewards weaker weapons instead of only blunting high-powered ones. In the scenario you describe, those Terminators have 2+ saves against AP-0 (fine), 2+ saves against AP-1 (fine), 2+ saves against AP-2 (fine), 3+ saves against AP-3 (fine), and 4+ saves against AP-4 (fine).

It doesn't make them more durable against AP-0 weapons, but nor did earlier editions – and I'm not seeking to address whether or not Terminators are good, just to resolve the weird situation whereby a Heavy Bolter, Krak Missile, and Plasma Gun all function normally against a Terminator... but Meltaguns and only Meltaguns run into a forcefield.

Ice_can wrote:
It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

Invulnerable saves aren't meant to be especially effective against light weaponry – they're meant to be universally effective against all weaponry, since your Wyches can backflip over a lascannon blast just as easily as a boltgun shell. It doesn't matter how strong the weapon is if it doesn't hit.

The only problem with this concept is that units with both armoured and invulnerable saves no longer flip between one or the other – they eat penalties on the former until they hit the latter. The problem isn't the invulnerable save itself – it's that units which used to be near-impregnable except to high-powered weapons are now more vulnerable, relatively speaking, to light armor-piercing guns. The problem is that light armor-piercing guns are totally untouched by your forcefield or holy aura or whatever, whereas in the past they were either affected (high enough AP to beat Armour) or couldn't affect you anyway (AP too low to beat Armour).

Ice_can wrote:
Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

At that point you might as well bump Invulnerable saves up a pip (i.e. 5+ becomes 6+) gamewide and let units take both in succession. 2+, reroll 1s, is +13%, and 2+ followed by 6+ is +16%. That's how Ward Saves used to work in WHFB – you roll Armour Saves, then Ward Saves. I don't recommend it, but it's certainly simpler.

Your not understanding what I mean

A terminator goes from 2+ 5++ to now 2+ rerolls 1, making 0AP spam esentially useless against them.

A Marine with a stormshield have 3+,3++ currently he would go to 3+ may reroll save rolls of 1,2,3. Ie you better have some AP or he' probably going to be fine.

Harliquins go from 6+,4++ to 6+ may reroll save rolls of 1&2.
They might need some rebalancing.

But the idea is to have the invulnerable save interact with your base armour save so you don't have the same mess we currently have.

Take the model everyone loves to hate.
A Castellen goes for 3+,3++, to 3+ may reroll 1,2&3.
So blasting away with mass lasguns is pretty bad return, bringing actual anti armour like -2AP, -3AP actually improved your odds against that big nasty target over just spamming Ap0

Again, that works fine (kinda) for armored models.

What about models that have Invulns INSTEAD of armor?

 JNAProductions wrote:

Ice_can wrote:
I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

So my Daemons get, instead of a 5++, a 6+ rerolling 1s? Or, if the weapon has any AP at all, they just don't get a save?

Yeah demons and Harliquins probably need some rebalancing like base 5+ Sv's but yes the idea is to try and move the balance away from spam all the S5 Ap-1 to actually bringing appropriate weapons.

That's a MASSIVE nerf to them.

Daemons, against AP0, get slightly more durable. But they take 20% MORE from AP-1, and 50% more from AP-2 or better.

Harlequins get it even worse. They're less durable against AP 0 with that change.

Ice_can wrote:

 JNAProductions wrote:

Ice_can wrote:
I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

So my Daemons get, instead of a 5++, a 6+ rerolling 1s? Or, if the weapon has any AP at all, they just don't get a save?

Yeah demons and Harliquins probably need some rebalancing like base 5+ Sv's but yes the idea is to try and move the balance away from spam all the S5 Ap-1 to actually bringing appropriate weapons.

...how does rerolling 1s make AP-1 specifically worse? It's just a general boost to the power of your Saves.

The version in the OP specifically addresses the gap between Armour and Invulnerable saves, without affecting units that already rely on Invulnerable saves.

RevlidRas wrote:

Ice_can wrote:

 JNAProductions wrote:

Ice_can wrote:
I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

So my Daemons get, instead of a 5++, a 6+ rerolling 1s? Or, if the weapon has any AP at all, they just don't get a save?

Yeah demons and Harliquins probably need some rebalancing like base 5+ Sv's but yes the idea is to try and move the balance away from spam all the S5 Ap-1 to actually bringing appropriate weapons.

...how does rerolling 1s make AP-1 specifically worse? It's just a general boost to the power of your Saves.

The version in the OP specifically addresses the gap between Armour and Invulnerable saves, without affecting units that already rely on Invulnerable saves.

The proposal I am responding to talks about REMOVING Invulns and replacing them with rerolls.

RevlidRas wrote:

Ice_can wrote:

 JNAProductions wrote:

Ice_can wrote:
I would rather leave all is dust alone and change the way invulnerable saves and armour interact.

Tour system leads to some very odd situation where a terminator in cover gets a 2+ vrs Ap0 to Ap-2, so mass Ap0 spam is still more effective against that heavily armoured unit.

Personally I think a better interpretation is units that currently have a 5++ gain reroll save rolls of 1, 4++ becomes reroll save rolls of 1&2, 3++ save becomes reroll saves of 1,2&3.

It hurts spamming Ap0 way more over actually having the right weapon where your paying for AP.

Rebalancing a bit the balance between hordes and elites and all makes invulnerable saves more effective against lighter weapons that heavier.

So my Daemons get, instead of a 5++, a 6+ rerolling 1s? Or, if the weapon has any AP at all, they just don't get a save?

Yeah demons and Harliquins probably need some rebalancing like base 5+ Sv's but yes the idea is to try and move the balance away from spam all the S5 Ap-1 to actually bringing appropriate weapons.

...how does rerolling 1s make AP-1 specifically worse? It's just a general boost to the power of your Saves.

The version in the OP specifically addresses the gap between Armour and Invulnerable saves, without affecting units that already rely on Invulnerable saves.

Because it doesn't change the game in anyway from what already happens, mass AP0 is still the most efficent way to remove everything. And vehicals without Invulnerable saves will be made even more redundant when GW inevitably increases AP to compensate.

All the while Infantry without invulnerable saves become even more and more prime targets for anti tank weapons while anti infantry if better against vehicals and monsters.

What about demons Harliquins moving from invulnerable saves to FNP's instead. As you shoukd be better able to dodge and absorb/defect weaker attacks but have a harder time against massive devistation weapons.

Maybe some invulnerable saves designed to represent something fundamentally different like harlequins get to keep them, but force fields etc change to the reroll style.

 JNAProductions wrote:
The proposal I am responding to talks about REMOVING Invulns and replacing them with rerolls.

Yes, I know. I was asking how that made AP-1 spam less effective, which is what was being claimed. As far as I can see, replacing invulnerable saves with re-rolls (setting aside the fate of units that only use invulnerable saves) is just a flat boost to all saves against all weapons.

It also doesn't actually do any of the things invulnerable saves are "meant" to do. An invulnerable save represents a kind of defence, like forcefields or bullet time dodging, that specifically isn't affected by the power of the weapon it's up against. A Sister of Battle has an invulnerable save because it matters not if her armour is sundered; lo, her faith may save her in her hour of need! And in older editions, this held true; either her armor was completely unaffected, or she got an invulnerable save. In this edition, her armour can be sundered just fine by heavy bolters, autocannons, krak missiles, and plasma guns, and her faith won't do a damn thing - unless her armour was specifically sundered by a meltagun, in which case it kicks right in.

(and now that I think of it, the OP fix doesn't really work for Sororitas, whose Shield of Faith isn't meant as a powerful armour boost...)

Re-rolling saves just makes armoured units, who are still subject to AP, even more armoured. It's got nothing to do with what invulnerable saves are meant for.

RevlidRas wrote:

 JNAProductions wrote:
The proposal I am responding to talks about REMOVING Invulns and replacing them with rerolls.

Yes, I know. I was asking how that made AP-1 spam less effective, which is what was being claimed. As far as I can see, replacing invulnerable saves with re-rolls (setting aside the fate of units that only use invulnerable saves) is just a flat boost to all saves against all weapons.

It also doesn't actually do any of the things invulnerable saves are "meant" to do. An invulnerable save represents a kind of defence, like forcefields or bullet time dodging, that specifically isn't affected by the power of the weapon it's up against. A Sister of Battle has an invulnerable save because it matters not if her armour is sundered; lo, her faith may save her in her hour of need! And in older editions, this held true; either her armor was completely unaffected, or she got an invulnerable save. In this edition, her armour can be sundered just fine by heavy bolters, autocannons, krak missiles, and plasma guns, and her faith won't do a damn thing - unless her armour was specifically sundered by a meltagun, in which case it kicks right in.

(and now that I think of it, the OP fix doesn't really work for Sororitas, whose Shield of Faith isn't meant as a powerful armour boost - it can be a FNP or something)

Re-rolling saves just makes armoured units, who are still subject to AP, even more armoured. It's got nothing to do with what invulnerable saves are meant for.

Except reroll 1's etc does represent some kind kf invulnerable saves well just not others.

A forcefield might not take the whole hit but it will take some of the hit out of heavier weapons while defelcting or absorbing all of weak shots.
2+ against Ap0 fails 1 in 6 saves
2+,5++ against Ap0 fails 1 in 6 saves

2+ against AP-3 fails 4 in 6 saves
2+,5++against Ap-3 fails 4 in 6 saves
Invulnerable save is useless even a 2+,3++ gets no bonus until it's taking Ap-2 or better.

2+ reroll 1's against Ap0 fails 1 in 36 saves
2+ reroll 1's against Ap-3 fails 3/6+(1/6*4/6) 60% of saves fail
3+, reroll 1,2,3 against Ap-1 fails 1/6+(1/2*2/3) 50% of saves fail.

Ice_can wrote:

Because it doesn't change the game in anyway from what already happens, mass AP0 is still the most efficent way to remove everything. And vehicals without Invulnerable saves will be made even more redundant when GW inevitably increases AP to compensate.

I don't think I can balance a homebrew fix concept against a hypothetical response by Games Workshop.

10 Tempestus Scions rapid firing at Terminators cost 90 points and will score 2.2 wounds. 20 Militarum Infantry rapid firing at Terminators cost 80 points and will score 1.1 wounds. That is half the effect for almost the same price (and you'd need two Orders to FRFSRF them).

Under my fix, the Tempestus Scions score only 1.5 wounds. The Militarum Infantry are unaffected, but still score only 1.1 wounds. AP weaponry is still desirable, but the force field of the Terminators means it has less of an impact on the game.

Under your suggestion, the Tempestus Scions score 1.1 wounds, and the Militarum Infantry score 0.5 wounds. AP weaponry remains twice as strong against Terminators. Nothing changed about how the game works, the Terminators just got tougher: you'd actually get the exact same result from just making them Toughness 5.

This fix isn't aimed at making Terminators more viable or fixing the current state of AP in the game or rebalancing Space Marines in general; that's beyond its scope. It's purely meant to solve the problem with Invulnerable saves that was introduced by 8e's granular armour saves - which it does.

The thing I don't like about current invulnerable saves + ignore 1ap is that it means your opponents are paying for useless upgrades more often.

Heavy bolters should be more effective than burst cannons vs armor.

At first the reroll thing seemed really scary but then started to show merits except for the acknowledged sore spots. The cool thing is that with rerolls before mods a 3+ rr123 fails on a roll of 3 against ap1 without a chance to reroll. It might make basic infantry weapons too bad though.

The other downside is that knights would be super weak to ap4. Maybe combine the two in alternating tiers?

Shas'O'Ceris wrote:
The thing I don't like about current invulnerable saves + ignore 1ap is that it means your opponents are paying for useless upgrades more often.

Heavy bolters should be more effective than burst cannons vs armor.

Okay, but... why? They never were in older editions. Your Sv represented your best chance of survival. It didn't scale upwards against weapons unable to pierce it.

Heavy bolters remain better than burst cannons against regular Marines. Their armour piercing qualities are just blunted against Terminators. It still takes three burst cannons to take one wound off a Terminator; they didn't become good against Termies, heavy bolters just got worse, because you now need four heavy bolters to wound a Terminator instead of two.

RevlidRas wrote:

Shas'O'Ceris wrote:
The thing I don't like about current invulnerable saves + ignore 1ap is that it means your opponents are paying for useless upgrades more often.

Heavy bolters should be more effective than burst cannons vs armor.

Okay, but... why? They never were in older editions. Your Sv represented your best chance of survival. It didn't scale upwards against weapons unable to pierce it.

Heavy bolters remain better than burst cannons against regular Marines. Their armour piercing qualities are just blunted against Terminators. It still takes three burst cannons to kill one Terminator; they didn't become good against Termies, heavy bolters just got worse, because you now need four heavy bolters to kill a Terminator instead of two.

Except a heavy bolter for killing terminators should be terrible, to stop one you need a power weapon or melta etc.
Should massed lasguns worry a stormshield equiped terminators not really according to lore and quite frankly terminators with stormshields even custodes suck pretty hard right now.
Same with almost anything with an armour save and invulnerable like you said.
Messing with Ap rewards using Ap0 against heavy armoured targets while punishing high Ap weapons.
That sounds like turning the game even more and more into most/cheapest wounds = guaranteed winner.
Thats not a direction that IMHO would be good for the game.

Ice_can wrote:

RevlidRas wrote:

Shas'O'Ceris wrote:
The thing I don't like about current invulnerable saves + ignore 1ap is that it means your opponents are paying for useless upgrades more often.

Heavy bolters should be more effective than burst cannons vs armor.

Okay, but... why? They never were in older editions. Your Sv represented your best chance of survival. It didn't scale upwards against weapons unable to pierce it.

Heavy bolters remain better than burst cannons against regular Marines. Their armour piercing qualities are just blunted against Terminators. It still takes three burst cannons to kill one Terminator; they didn't become good against Termies, heavy bolters just got worse, because you now need four heavy bolters to kill a Terminator instead of two.

Except a heavy bolter for killing terminators should be terrible, to stop one you need a power weapon or melta etc.
Should massed lasguns worry a stormshield equiped terminators not really according to lore and quite frankly terminators with stormshields even custodes suck pretty hard right now.
Same with almost anything with an armour save and invulnerable like you said.
Messing with Ap rewards using Ap0 against heavy armoured targets while punishing high Ap weapons.
That sounds like turning the game even more and more into most/cheapest wounds = guaranteed winner.
Thats not a direction that IMHO would be good for the game.

This mechanic doesn't make AP-0 weapons any better. It just makes Terminators, Possessed, and similar units more durable against AP-1, AP-2, and AP-3 weapons - like they used to be. And as we've seen, AP-2 weapons (e.g. Infantry vs Special Weapons Plasma or Tempestus Scions) are still more effective than AP-0 weapons point-for-point against a 2+ save. And since almost no armies consist entirely of 2+ models with an invulnerable save, AP-1 weapons still have a place.

Now, are massed, low-Strength AP-0 weapons unintuitively good point-for-point against models with high Toughness and/or Sv? Almost certainly! But that's a completely separate problem. It has nothing to do with Invulnerable saves (in this edition or otherwise) and you can't (and shouldn't) solve it by meddling with them. That's why it's outside the scope of this fix.

For example, if you give most Vehicles a rule like this:
"Tank Armour: Subtract 1 from rolls to wound this model using a weapons with a Damage characteristic of 1."

It becomes impossible for Lasguns to wound T6+ vehicles, and even Pulse Rifles and Boltguns start wounding them on a 6+ (or not at all for Boltguns against T8+), while more typical "tank" weapons are left unaffected.

Lightly-armoured or open-top models like Sentinels, or Monsters that could be vulnerable to massed light fire can instead get something like:
"Light Tank Armour: Add 1 to this model's saving throws against weapons with a Damage characteristic of 1."