Rifle Cannon Math

[Daryk]

For quite some time now, I've been advocating for a change to how Rifle Cannons work.  The flat -3 to damage for them (regardless of size) results in ZERO damage for the Light (a singularity that is anathema to any game system).  I propose the Heavy take -4 (resulting in 5), the Medium take the canonical -3 (resulting in 3), and the Light take only -2 (resulting in 1).  The math backing that up is below, based on the AToW page 211 and AToW Companion page 171 formulas.  I could have sworn I posted this math before, but I can't find it.  7 AP for the Rifle Cannons is based on them being able to defeat Tech Level C "state of the art" armor, which was BAR 7.

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Heavy
Assuming 7AP/54BD (6 points BD per 1 point TW scale damage per AToW page 211):
Assuming "splash damage" ammunition and a single shot while using the AToW Companion page 171 formula:
Penetration Factor: 7 AP / 4 = 1.75
Damage Factor: 54 BD * (3.5 + 1 for "splash damage") = 243
TW Damage = PF * DF / 50 = 8.51, rounds to 9 points of TW damage

7 AP is 3 points below 10 BAR, so both AP and BD are reduced by 3 (per AToW page 185), to 4 AP and 51 BD against BAR 10:
Assuming "splash damage" ammunition and using the AToW Companion page 171 formula:
Penetration Factor: 4 AP / 4 = 1
Damage Factor: 51 BD * (3.5 + 1 for "splash damage") = 229.5
TW Damage = PF * DF / 50 = 4.59, rounds to 5 points of TW damage (-4 compared against BAR 7)

Against BAR 8: 6 AP / 53 BD yields 7.16 points of damage, rounding to 7 (-2 compared against BAR 7)
NOTE: The above shows how finely "tuned" the HRC was to the armor of its time.
Against BAR 9: 5 AP / 52 BD yields 5.85 points of damage, rounding to 6 (-3 compared against BAR 7)

Medium
Assuming 7AP/36BD (6 points BD per 1 point TW scale damage per AToW page 211):
Assuming "splash damage" ammunition and a single shot while using the AToW Companion page 171 formula:
Penetration Factor: 7 AP / 4 = 1.75
Damage Factor: 36 BD * (3.5 + 1 for "splash damage") = 162
TW Damage = PF * DF / 50 = 5.47, rounds to 6 points of TW damage

7 AP is 3 points below 10 BAR, so both AP and BD are reduced by 3 (per AToW page 185), to 4 AP and 33 BD against BAR 10:
Assuming "splash damage" ammunition and using the AToW Companion page 171 formula:
Penetration Factor: 4 AP / 4 = 1
Damage Factor: 33 BD * (3.5 + 1 for "splash damage") = 148.5
TW Damage = PF * DF / 50 = 2.97, rounds to 3 points of TW damage (-3 compared against BAR 7)

Against BAR 8: 6 AP / 35 BD yields 4.73 points of damage, rounding to 5 (-1 compared against BAR 7)
Against BAR 9: 5 AP / 34 BD yields 3.83 points of damage, rounding to 4 (-2 compared against BAR 7)

Light
Assuming 7AP/18BD (6 points BD per 1 point TW scale damage per AToW page 211):
Assuming "splash damage" ammunition and a single shot while using the AToW Companion page 171 formula:
Penetration Factor: 7 AP / 4 = 1.75
Damage Factor: 18 BD * (3.5 + 1 for "splash damage") = 81
TW Damage = PF * DF / 50 = 2.84, rounds to 3 points of TW damage

7 AP is 3 points below 10 BAR, so both AP and BD are reduced by 3 (per AToW page 185), to 4 AP and 15 BD against BAR 10:
Assuming "splash damage" ammunition and using the AToW Companion page 171 formula:
Penetration Factor: 4 AP / 4 = 1
Damage Factor: 15 BD * (3.5 + 1 for "splash damage") = 67.5
TW Damage = PF * DF / 50 = 1.35, rounds to 1 point of TW damage (-2 compared against BAR 7)

Against BAR 8: 6 AP / 17 BD yields 2.3 points of damage, rounding to 2 (-1 compared against BAR 7)
Against BAR 9: 5 AP / 16 BD yields 1.8 points of damage, rounding to 2 (-1 compared against BAR 7)

[RifleMech]

I'd certainly prefer the LRC doing some damage than none. I'm having trouble with the math though. ATOW says that the BD is 6 times the TW damage. For a Heavy Rifle Cannon against BAR8-10 armor that would be 36. Right? 6x6=36 As the damage done against those armors is 6. 

When I do the math for the HRC 7AP/36BD against BAR10 armor I get 5.67, rounded to 6.
For the Medium Rifle Cannon (7AP/18BD) I get 2.83 rounded to 3.
For the Light Rifle Cannon (7AP/0BD) its 0 damage. Against Internal Structure, BA, etc. I get I get 2.83 rounded to 3. That's keeping the reduced AP though.

When I do full damage I get
HRC (10AP/54BD) = 12.15 rounded to 12
MRC (10AP/36BD) = 8.1 rounded to 8
LRC (10AP/18BD) = 4.05 rounded to 4.

So to me, if I did all the math right, the listed damage for Rifles has already been reduced to start with. The -3 damage reduces them even more. Do I have this right?

[Daryk]

I forgot to cite AToW page 185.  That's where the step that reduces AP and BD by 3 comes from.  I'll edit that in shortly.

The Rifle Cannons don't do "full" damage against BAR 10 armor.  My assumption is that they are AP 7 weapons, and that's what I use with the AP vs. BAR system.  Because AP 7 is 3 points below BAR 10, both AP and BD are reduced by 3, yielding the math in the first post.

Here's a hopefully clearer summary of the results:

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BAR: 7 & < 8 9 10
Heavy   9 7 6 5
Medium   6 5 4 3
Light   3 2 2 1


[monbvol]

Unfortunately this is really starting to show that the conversion in AToW Companion is not really meant to be used this way and that there are at least two separate BAR systems in Battletech.

Case in point a Large Laser does not do more damage against BAR 9 or lower armor but is clearly an AP 10 weapon.  Even page 211, possibly 212 I'm away from my books to double check, of AToW indicates when shooting at something with a Large Laser that isn't an AToW character you defer to TW/TacOps rules/procedures.

But going the other way an AToW character armed with a Autorifle using AP ammo is going to do more damage against a BAR 9 target under AToW's rules.

[Daryk]

A Large Laser against something with less than BAR 8 gets a free crit check, though.

And I believe it won't take that much to tweak the systems to finally give us one formula that works from top to bottom that rounds to the current values at each scale.

[RifleMech]

That's where I'm confused though. Rifles are the only weapons that function this way. Their AP isn't reduced against Internal Structure, Battle Armor, Buildings or other things. Just BAR8-10 Armors. The thing is going by the math Rifles have a AP of 7 against everything. Even when their BD isn't reduced.  7AP/54BD converts to 9 points of damage. That's what HRC does against BAR7 armor and every other target they don't suffer a -3 against. They're not doing the full 10AP that ATOW says Vehicular Scale Weapons should do. If they did, the HRC would do 12 points of damage against those targets. The MRC would do 8 points of damage and the LRC would do 4 points.

This is what I get at full ATOW conversions and full TW damage as listed in TO.
HRC (10AP/54BD) = 12.15 rounded to 12
MRC (10AP/36BD) = 8.1 rounded to 8
LRC (10AP/18BD) = 4.05 rounded to 4.

This is what I get with ATOW conversions Vehicle Scale = 10AP and the -3 TW damage. Based on Rifles TO listed damage.
HRC (10AP/36BD) = 8.1 rounded to 8
MRC (10AP/18BD) = 4.05 rounded to 4.
LRC (10AP/0BD) = 0 rounded to 0.

This is what I get when using 7AP and TO listed "full" damage.
HRC (7AP/54BD) = 8.505 rounded to 9
MRC (7AP/36BD) = 5.67 rounded to 6
LRC (7AP/18BD) = 2.835 rounded to 3.

This is what I get when reducing the AP and including the -3 damage. The Official TO damage against BAR-8+ Armors.
HRC (7AP/36BD) = 5.67 rounded to 6.
MRC (7AP/18BD) = 2.83 rounded to 3.
LRC (7AP/0BD) = 0 damage

The last two are the Official damages for Rifles with and without the -3 damage.  If I'm right, Rifles are being nerfed against all armors.

None of those figures include splash damage either. If it's included then the "full" damages would be
HRC (10AP/54BD) 14.85 rounded to 15
MRC (10AP/36BD) 9.9 rounded to 10
LRC  (10AP/18BD) 4.95 rounded to 5

So something is wonky.

[Daryk]

The wonkiness is the arbitrary -3 at the TW scale.  That's what I've been saying.  I assume they have an AP of 7 because BAR 7 is where there's no penalty.  In my opinion, they should have just set them to 1/3/5 (Light/Medium/Heavy) damage and call it good.  If anything should have a special rule, it would be their "improved" performance against BAR 7 and below.

[Maingunnery]

What if the AP is 6?

[Daryk]

If it's 6, you'd reduce the AP and BD by 4 against BAR 10.  That would yield 3.38 (rounding to 3) for the Heavy, 2.16 (rounding to 2) for the Medium, and 0.95 (rounding to 1) for the Light.

[monbvol]

According to AToW all mechscale weapons have a 1 meter splash effect.  Can't remember if that is radius or diameter off top of my head and still stuck at work.  Either way there is no minimum area of effect to qualify as splash given in the formula.

All this math as interesting as it may be is honestly just more proof that the conversion formula is not the basis to start from as it is too heavily flawed for bidirectional conversion.

[Daryk]

The splash effect is accounted for in the math above.

And as I said in the other thread, if TPTB had avoided the singularity of ZERO damage for the LRC, we wouldn't even be having this discussion.

The AToW Companion formula works just fine... if anything is flawed, it's the 10AP/6xTW Damage BD equation.

[TigerShark]

I hate the Rifle (Cannon) rules. They are "suspension of disbelief" breaking weapons. Am I to believe that an "Assault Rifle" from an infantryman does 0.54 damage, but a hit from a tank shell does ZERO?! That's insane. It would be better fixed by most infantry small arms doing 0 damage, but if you go the other way, than the Light Rifle (Cannon) should do SOMETHING. Let's assume it's a 120mm APFSDS shell with a common core that isn't tungsten. Something that won't penetrate "modern" armor. And that the "Heavy Rifle" is 200mm or something with a tungsten core.

Either way, they'd do SOME damage v 'Mechs. Or, if they're immune, then infantry rifles should do 0. Either way..... this makes no sense.

[Daryk]

I advocate for LRCs to do SOME damage vice nerfing all infantry for the rest of time.

[Maingunnery]

I advocate for LRCs to do SOME damage vice nerfing all infantry for the rest of time.

Why not both?

[Daryk]

Because infantry should be able to do SOME damage too...

[Maingunnery]

Because infantry should be able to do SOME damage too...

Sure but that should be more of the role for disposable secondaries, such as SRM launchers instead of infantry rifles.

[Daryk]

TPTB built quite the system to allow 31st century Auto-Rifles to damage BAR 10 armor.  I think it does its job just fine.  Rifle Cannons were a later add that throws a wrench at that system.

[TigerShark]

I advocate for LRCs to do SOME damage vice nerfing all infantry for the rest of time.

They should. Just from the squad weapons, like a Support PPC.

[Daryk]

Support PPCs are their own very special kettle of fish.

[TigerShark]

Sorry about the thread drift to infantry weapons, BTW. I just feel it's relevant to the point of WHY Rifle (Cannon)s should have some kind of errata. BAR 10 armor was supposed to be revolutionary. So advanced, in fact, that it could stop tank rounds entirely. That same armor should not be able to be damaged by a 5.56 round from an AR-15 if 120mm shells are bouncing off.

It's a "one or the other, but not both" scenario. If you have to make Rifles do more damage, then good. That'd work at my table, for sure.

[Daryk]

No worries!  The infantry weapon question is part and parcel of the debate.  For the record, individual 4AP/4BD shots will round down to zero against BAR 10.  Both the burst fire modifier and the abstraction of infantry units is what gets the bog standard Auto-Rifle into "pay attention" territory for BattleMechs.  Conventional infantry still has to hit (not easy with 1/2/3 range for just Auto-Rifles), then roll on the cluster hit table, THEN break up whatever damage gets through into 2-point groups.  Penetration is extremely unlikely, but not impossible.  And I think that's exactly what it SHOULD be.  Which is why I'm absolutely in the camp that says the LRC should do 1 point of damage, not ZERO.

[monbvol]

The splash effect is accounted for in the math above.

And as I said in the other thread, if TPTB had avoided the singularity of ZERO damage for the LRC, we wouldn't even be having this discussion.

The AToW Companion formula works just fine... if anything is flawed, it's the 10AP/6xTW Damage BD equation.

Except to make the equation even begin to work more than the BD of mech weapons needs changed.

I know.  I tried.

[Daryk]

My experience so far is that it works well enough at 10 TW damage and below.  I agree it goes off the rails completely above that.

[RifleMech]

Looks like my previous reply disappeared.


I can't say I'd be in favor of infantry doing no damage. That'd end up meaning that platoons of infantry with auto-rifles couldn't dent the family car. Infantry need some work but I don't think that's it.

Back to Rifle Cannons, I understand what TPTB were trying to do but it goes too far, isn't consistent with other pre-spaceflight weapons, isn't consistent against other advanced armors, and causes problems. Just looking at the math, I think Rifles are already bad enough without the -3 damage, and the extra penetrating critical hit roll for the heavy.

[Daryk]

The inconsistency is exactly why I've been harping on this issue for ages.  TPTB had already established the conversion formula (even if they hadn't shared it with us yet) when they introduced Rifle Cannons.  There's simply no excuse for introducing a singularity that late in the process.

[Charistoph]

Sorry about the thread drift to infantry weapons, BTW. I just feel it's relevant to the point of WHY Rifle (Cannon)s should have some kind of errata. BAR 10 armor was supposed to be revolutionary. So advanced, in fact, that it could stop tank rounds entirely. That same armor should not be able to be damaged by a 5.56 round from an AR-15 if 120mm shells are bouncing off.

It's a "one or the other, but not both" scenario. If you have to make Rifles do more damage, then good. That'd work at my table, for sure.

The only reason I ever thought it was near workable is a combination of the nature of the new armor and the high volume of Infantry rifle fire.  Our "modern" armor is designed to counter penetration, just like most infantry rifles (and a lot of anti-armor rounds) are designed around penetration.  Battletech armor is ablative, which prevents most penetration by transferring that energy in to breaking off those scales of armor.

The Rifle rounds and big and explody, but designed for penetrative power in a single hit.  The Autorifle rounds are equally designed for penetration, but there are a LOT of them being used to dislodge those scales of armor, so their quantity takes on a quality all its own.  To use another game's reference, it is why a squad of 40 Space Army Conscripts scares the hell out of Space Marine Terminators.

It's the only way I could make it work.

[RifleMech]

The inconsistency is exactly why I've been harping on this issue for ages.  TPTB had already established the conversion formula (even if they hadn't shared it with us yet) when they introduced Rifle Cannons.  There's simply no excuse for introducing a singularity that late in the process.

I've never liked it either. It's always bugged me that weapons do X damage in the RPG and Y damage in the boardgame. The Rifles just make things worse because they aren't consistent with either rule set.

Looking at the math also has me asking myself, why convert XTRO:1945 weapons to "modern" battletech equivalents, when their listed damage puts them right among Rifle Cannons now. It also reminds me that Herb had the 120mm Cannon doing 12 points of damage. Which is what my math came out to for a HRC doing full damage when converted to AToW. But that might be a different topic. 

[TigerShark]

The only reason I ever thought it was near workable is a combination of the nature of the new armor and the high volume of Infantry rifle fire.  Our "modern" armor is designed to counter penetration, just like most infantry rifles (and a lot of anti-armor rounds) are designed around penetration.  Battletech armor is ablative, which prevents most penetration by transferring that energy in to breaking off those scales of armor.

The Rifle rounds and big and explody, but designed for penetrative power in a single hit.  The Autorifle rounds are equally designed for penetration, but there are a LOT of them being used to dislodge those scales of armor, so their quantity takes on a quality all its own.  To use another game's reference, it is why a squad of 40 Space Army Conscripts scares the hell out of Space Marine Terminators.

It's the only way I could make it work.

It sounds reasonable. Absolutely. But with a Light Rifle doing 0 damage, that means 10,000 of them still do 0 damage. I appreciate the logical reasoning, though. lol I think of that stuff too.

[Daryk]

That's exactly why zeros and infinities are so bad for game design.

[RifleMech]

What makes the situation even more bizarre is that a mech could throw a ton of LRC ammo at a BAR-10 armored target and do more damage than any number of LRC would actually firing at the target.