I've been unsatisfied with how macrocannons outperform lances.  So I've done an awful lot of calculations to try and find house rules that change the game in a favorable manner and make the choice of lance vs. macro interesting.

Here's what I've worked out:

Armour should count against each macrocannon hit, but armour should be reduced to account for the change.  Specifically armour should be reduced by 12.  That makes an armour 15 Raider have an armour of 3, an armour 17 Frigate gets an armour of 5, and an armour 20 Cruiser has an armour of 8.

The value 12 was chosen because the breakeven point between lances and macros with this rule is between 6 and 7.  With an armour of 6, Dual Sunsears deal more damage than a Titanforge Lance and a Mars Macrocannon.  Once armor reaches 7, the lance is more effective.  By reducing armor by 12 that makes lances only worthwhile against the heaviest frigates, light cruisers, and cruisers.

It takes a little longer to figure damage, but it also makes armour work more like it does in personal combat.

Making this change to the rules does a few different things:

Armour is in general more effective when it gets up to high numbers.  Raiders take a little bit more damage than the RAW, but cruisers, particularly with armoured prows, are nigh invulnerable to macrocannon fire.

The influence of Ballistic Skill on damage is reduced.  This hardly means that BS doesn't matter; you still do more damage as your BS goes up, but the rate at which it increases is slower.  This means that NPC ships can still do respectable damage and your Voidmaster won't blow up everything in a single volley.  Say your ship is equipped with dual Mezoas and is firing on a frigate.  If your BS is 50 the expected damage is virtually unchanged between these rules and the RAW (7.38 vs 7.52), but with a BS of 30 you deal twice as much damage as you deal with the RAW (2.48 vs 1.12).  However, at BS 70 you deal less damage than you would with the RAW (12.56 vs 15.79)

High plus weapons like Ryzas and Pyros effectively become armour piercing, i.e. their relative effectiveness increases as armour increases.

Lances deal more damage against cruisers.  This was the effect these house rules were intended to make and they achieve that without any other changes to how lances or macrocannons work.

Under this system a single cannon has a better chance to deal damage.

Mars Cannons aren't quite so bad.

Other things to consider:

If you change broadsides so that they inflict double the amount of hits (essentially giving them Storm), but reduce their strength to 3 (or 4 in the case of 1d10+1 Sunsears), they work better with this system.  They are also much more capable in the hands on NPC ships without becoming too overwhelming in PC hands.  They are downright frightening to lightly armoured ships though, but that seems acceptable.

Reducing the damage torpedoes deal by 12 makes them function identically under this system as they function in the RAW.

The effectiveness of bombers is subtly changed, and probably requires further examination.  Their damage per hit may need to be reduced.

Reducing Sunsears to 1d10+1 makes them an interesting choice, rather than straight up better than Mars or Heculators. They deal more damage against lightly armoured opponents, but less against heavily armoured ones.

Since armour is more effective, bonuses to armour probably shouldn't stack.  Adding Excess Void Armour, Armour Plating, and a Reinforced Prow together can make even lightly armoured craft extremely resistant to macro fire.  Excess Void Armour may be too powerful all by itself.

Some alien races use variant rules that change effectiveness under this system.  Rak'Gol macros probably need adjusting to deal enough damage.  Eldar are even more fragile than they were and may need a small armour increase or some other change to compensate.

Very interesting idea and a novel take on the problem. Might indeed be worth a try, I will see how it works out in some simulations.

                                                          Friedrich van Riebeeck, Navigator Primus, Heart of the Void

I like the idea, but I'd really like to know how to balance out bombers before making any changes.

I love your suggestions Moribund.

Concerning  the bombing runs, I do find them as written a bit lacking RAW, unless your target is 6VU away or less. I'd let their damage as written.

Hmm, Bombers are fairly balanced in this system if you combine all your squadrons into one wing.  They deal significantly more damage if you only have a single squadron per wing.

I ran numbers for differently armed NPC ships of the same class fighting one another.  A Dauntless-class light cruiser (LC) equipped with Mars Broadsides and a Prow Mars Cannon vs. one equipped with Jovian Escort bays and a Prow Ryza Cannon (The space/power requirements are equivalent).  

The Lunar-class cruiser (C) is equipped with either Mars Broadsides or Jovian Landing bays.  I assume the Prow contains nothing relevant, like a Torpedo Launcher, to simplify my math.

The MC column is the average Damage Per Round for the Macrocannons.  ES is bombers against an equally skilled opponent , and CC is against a competent crew.  CS is combined squadrons and SS is single squadrons.

% indicates crew rating, all squadrons consist of only bombers, and I'm using my suggested broadside rules.

LC MC ES-SS CC-SS ES-CS CC-CS
30% 1.94 2.77 2.77 2.38 2.38
40% 3.09 4.09 4.65 3.42 3.75
50% 4.28 4.79 6.36 4.06 4.96
60% 5.49 4.87 7.90 4.31 5.99
C
30% 1.36 6.05 6.05 3.95 3.95
40% 2.30 8.40 10.08 4.66 4.79
50% 3.28 9.41 14.11 5.38 5.63
60% 4.30 9.07 18.14 6.05 6.47

18 damage per round with an elite crewed cruiser, ouch!  If you don't have a good crew, single squadrons tear you up.  It's not that terrible though, because there is a balancing factor.  Using single squadrons makes your bombers much more likely to get shot down, so you won't be making many runs at full strength.  You'd have a 40% chance that at least half your squadrons were shot down with that run.  As opposed to the 0% chance that more than two squadrons were shot down with a combined wing.

As it costs a lot to get/repair/  bombers & fighters, even if single runs are more deadly, I'm not sure players will use that.  You can't easily resupply in pilots and small crafts when you are in the middle of nowhere, exploring  unknown systems.

Your % are based on your new armour system, I suppose ?

A great modification to the Armour system. I like it.

So we're now left with the question of how Torpedoes are affected by this. The obvious choice is to simply drop their damage by 12 and continue using the rules as written- but the maths you've used might show some deep flaw in that idea so I'll wait to hear what results they get.

All of my above numbers were using the armour house rules.  With the original rules, it's generally more effective to combine bombers into one big wing than to break out into single squadrons, so you don't really run into that dilemma of choice.

Getting hit with a bunch of individual bombers means certain death for a Raider (like 60 points of damage death), but my broadside rules are also extremely deadly to Raiders.

If the bomber damage still seems too high for you, reducing the damage per bomber hit drops the above 18.14 damage to 12.96 for 1d10+3 and 8.64 for 1d10+2.

The 1d10+2 seems like too much of a nerf, the light cruiser doesn't deal as much damage as the macros even with single squadrons.  I didn't run the full numbers on 1d10+3, but that seems like a happy medium for the numbers I looked at.

But you also have to keep in mind that the game changes a little when you introduce PCs into the equation, because bomber runs are based on Command tests, which are easier to raise than Ballistic Skill.

This rule change does absolutely nothing to Torpedoes if you subtract 12 from their damage.  It does feel really weird to roll 2d10-7 for Vortex torpedoes, but the math is identical.  I'm not saying that torpedoes are balanced, but this doesn't make them any more or less so.

torps should be scary. After all, you have to pay every single one of them. The same for the Nova Cannon...

 These rules sound like a really great solution to the macrocannon/lance/armor problem and the ease of conversion to the new rules has an elegance that appeals to me. I'll have to test these out in game.  

 So let's look at torpedoes and see if they are scary.

I did damage calculations for each type of torpedo. Plasma (P), Boarding (B), Melta (M), Virus (V), and Vortex (X).  For Boarding and Virus I listed the chance the effect will go off per torpedo, and the others are damage per torpedo against different armour values.

15 17 20
P 12.10 10.10 7.12
B 99% 96% 80%
M 13.40 11.40 8.42
V 96% 87% 64%
X 3.90 2.40 0.79

Note that this is just damage per hit, not damage per round so it doesn't include Ballistics Skill, Guidance, Enemy Crew Rating, Enemy Turret Rating, or Salvo Size.  I also don't factor in critical hits which will improve damage, particularly in the case of Vortex torpedos with their 75% crit chance.

All this to say, I think torpedos are fine.  Though I'm not sure Meltas are really worth the cost damage wise, and Vortex torpedoes are just quirky.

(Meltas do have an increased chance of inflicting crits: 28% vs. the plasma's 13%)

I like this concept.  Simple and ellegant solution.  The idea of halving the strength of broadsides but granting them storm is an interesting one.  I was becomming tempted to class batteries as semi-auto fire (+10 to hit, 1 bonus hit per 2 degrees of success) and broadsides as full auto fire (+20 to hit, 1 bonus hit per degree) to reflect the saturation of fire meaning that you should be able to hit with something.

I think your math on Vortex torps might be a bit out.  They ignore armour.  Shouldn't they be imune to your proposed -12 damage for torps due to this?

 Oh, I missed the rule on Vortex Torpedos ignoring armour.  That makes their damage make WAY more sense.  Weirdly tacked on in a paragraph about Morale damage, though.

They would deal 2d10+5 damage then regardless of armour (or any house rules that alter armour) for an average damage of 18.5.

The text implies that all Vortex torpedos inflict a critical hit, but the way Terminal Penetration works doesn't guarantee that they do.  Do you think they changed Terminal Penetration to its current form after they wrote that?

I examined semi-auto before I settled on this rule.  Those changes severely limit the damage NPC crews can inflict, and put more emphasis on Ballistic Skill than the original rules.  A competent crew with dual sunsears inflicts an average damage per round of just 0.44 against armour 15.  When you get up to 70 BS, the DPR increases to 10.79.

My rules give you 2.48 and 12.56 respectively.  A five fold increase rather than a twenty-four fold increase.

The vortex torp rules are a little more... obscure to find than most.  Glad to help.

And thankyou for the SA/FA math!  Consider that thought dropped well and truly!  I guess what I am after is a method of making "normal" BS broadsides better than a battery.  Your storm rule should do that, but I am still leaning towards a bonus to hit with broadsides instead.

If I could be so bold as to request a math-hammering, how does a sunsear battery at BS 40 compare to a Sunsear broadside (half str and storm) and a broadside (full Str, no storm, +20 to hit).

Edit: Hmmm....  My tables aren't set up to give me accurate values for a single weapon.  Let me get back to you.