Rotary vs. Ultra

[Stinger]

Okay, I have a question to pose here:

I recently got a Deimos mini as a gift, and it got me thinking.  What would be better (ignoring tonnage) 3 Clan Ultra-ACs or 1 Clan Rotary AC.  Let's say we are talking about the Rotary AC-2.

What advantage would 3 CUAC2s have over a single CRAC2?

Edit: Updated to reference Clan versions of the weapons.

[martian]

Okay, I have a question to pose here:

I recently got a Deimos mini as a gift, and it got me thinking.  What would be better (ignoring tonnage) 3 Ultra-ACs or 1 Rotary AC.  Let's say we are talking about the Rotary AC-2.

What advantage would 3 UAC2s have over a single RAC2?

If nothing else, UAC-2 has better range than RAC-2.

[Stinger]

If nothing else, UAC-2 has better range than RAC-2.

Sorry! I was thinking Clan Rotaries.  I will update the original post to specify.  Though the Clan UAC 2 does have a slight advantage.

[martian]

Sorry! I was thinking Clan Rotaries.  I will update the original post to specify.  Though the Clan UAC 2 does have a slight advantage.

That's what I meant.

You can unjam the RAC-2 during a game, but you can't unjam UAC-2.

[Wildonion]

There is also some system redundancy, for if you start taking arm damage or suffer a floating critical. That said, the weight savings gained from the switch is more than enough to convince me that you are better off with a RAC 2 in each arm.

**EDIT** Oh and with the RAC 2 you get the advantage of only having to roll once for each weapon at easy target numbers and the disadvantage of only getting to roll once for each weapon at high target numbers. With six UAC 2's, you are bound to hit something at long range and bound to miss something at short range.

[Top Sergeant]

Logistics are easier for the UAC 2 if you're on a limited ammo budget.

[Arkansas Warrior]

Okay, I have a question to pose here:

I recently got a Deimos mini as a gift, and it got me thinking.  What would be better (ignoring tonnage) 3 Clan Ultra-ACs or 1 Clan Rotary AC.  Let's say we are talking about the Rotary AC-2.

What advantage would 3 CUAC2s have over a single CRAC2?

Edit: Updated to reference Clan versions of the weapons.

Well, a CRAC-2 weighs 8 tons, three CUAC-2s weigh 15 tons.  I'd rather have the extra 7 tons of other stuff.

[Diablo48]

The UAC 2's also provide more damage and reliability at high TNs because you do not want to risk a jam by double tapping.

[Stinger]

Another thing I was thinking was ammo effeciency, at least at short range.  When you are at close range, and you are firing 3UACs, and lets say they all hit, or with the RAC, it also hits.  The UACs firing in standard mode are guaranteed to get 3 hits, and between 3 and 6 for ultra mode, but the RAC is going to need to fire 5 rounds to average 3, and 6 just to average 4, with probabilities being lower.  So would I be correct in saying you need to use 5 rounds to get the same effect as a UAC firing in normal mode?

[Arkansas Warrior]

Assuming no other weapons though, I can use the 7 tons I saved to add a 2 ton TC (making hit probability more likely to begin with), and 5 extra tons of ammo, so I've got plenty to burn.  Of course, the odds of a mech armed only with a CRAC 2 or three CUAC 2s is exceedingly low, and I'd argue the RAC wins there as well, because you can use those saved tons for more armor, a bigger engine, jump jets, back up guns, or any number of other things.

[Stinger]

So, using the deimos as an example, with the Prime config having 6 UAC2s (or other mechs, such as the Jupiter, with 4 UAC5s) the weapon is essentially, completely outclassed but the Rotary autocannon, with the exception of a minor amount of range (at the disadvantage of a minimum range).  Am I right?

[CloaknDagger]

Okay, I have a question to pose here:

I recently got a Deimos mini as a gift, and it got me thinking.  What would be better (ignoring tonnage) 3 Clan Ultra-ACs or 1 Clan Rotary AC.  Let's say we are talking about the Rotary AC-2.

What advantage would 3 CUAC2s have over a single CRAC2?

RAC2, easily.

The thing is, Ultras are bad, and of the ultras, the UAC2 is the worst. Think about it, with a UAC20, you have a significant chance to jam, but you get 20 damage out of it. But with a 2, it's the same chance to jam, but the benefit is literally 1/10th as much.

So RAC2 wins by being able to be unjammed.

And, you know, 3xUAC2s weight 15 tons, and the RAC2 is only 8 tons, so with some good overhauling, you can actually have 2xRAC2s. And have it be a viable main weapon. (Though I must recommend an ERPPC next to it.)

[Col Toda]

The problem I always had with RAC is Ammo consumption .  A RAC 5 uses up an average of 5 shot / turn that means going though a ton of ammo every 4 turns . The RAC2 is a little better with 9 turns but I have seen a model of linebacker that has 2 RAC2s and runs though all its ammo at ruinous rate . As far as I am concerned a light AC / 5 with precision ammo is best and the ultra 10 and 20 is almost as good the RAC just does not give enough return for the ammo use.

[Arkansas Warrior]

Where do you come up with that average?  It seems awfully high to me.

[snewsom2997]

The problem I always had with RAC is Ammo consumption .  A RAC 5 uses up an average of 5 shot / turn that means going though a ton of ammo every 4 turns . The RAC2 is a little better with 9 turns but I have seen a model of linebacker that has 2 RAC2s and runs though all its ammo at ruinous rate . As far as I am concerned a light AC / 5 with precision ammo is best and the ultra 10 and 20 is almost as good the RAC just does not give enough return for the ammo use.

I try to load 3 Tons for RAC/5's and 2 Tons for RAC/2's. When I custom build a mech. I tend to stick to 4 round bursts, so 60 shots lasts 15 Rounds, on the RAC/5's, RAC/2's are less of an issue.

[Col Toda]

I normally see 5 round burst as 6 rounds makes jamming risk too high . Even a 4 round burst that brings the total to 5 Combat Turns  instead of 4  Combat Turns per ton for and AC/5 . I still think you can get more out of 2 light AC 2 s with a targeting computer and precision rounds than I could get out of 1 RAC 2 .  I believe if 2 Light AC 2 hitting 80+% of the time is better than
1 RAC2 hitting 20% of the time or less is better .

[sebster]

In answering a question like this, the first and most important question to ask is, for the given tonnage, how much damage can I expect to do each turn.  Which in this case is built around this little table;

Two shots - 1.42
Three shots - 2.00
Four shots - 2.64
Five shots - 3.17
Six shots - 4.00

That's showing the average number of hits you can expect on the first six columns of the cluster hits table.

This means three UAC2, assuming three hits, will average 4.26 hits.  RAC2, firing the optimum five burst, will average 3.17 hits.  So, basically, for eight tons of RAC you get three hits, while 15 tons of UAC gets you four hits per turn.  Seven more tons for one more hit is a pretty bad deal.

Admittedly, that deal is offset slightly by the slightly longer range of the UAC and the slightly greater risk of jamming suffered by the RAC firing fire rounds a turn (3 times as great as any of the UAC being jammed).  But those advantages can't really justify an extra seven tons in weapons.

[CloaknDagger]

The problem I always had with RAC is Ammo consumption . 

That's the OPPOSITE of a problem.

If you run out of ammo, it mean you shot it all at the enemy.

Remember, it gets the same ammo per ton as regular ACs, about 100 damage. So if you run out faster, than means you would still be firing a regular AC, and thus, the enemy would have less damage right now, and thus, they would be working at closer to full strength, and thus, you would be getting hit harder right now.

[Col Toda]

Your point is taken ; however a RAC/2 averages about 6 pt / hit and say hits 1/2 the time . 3 light AC2 w targeting computer and precision ammo averages 4 and hits almost all the time .  The RAC runs though a ton firing 5/shot about 9 rounds while three
Light AC/2 with precision rounds fire though a ton in 7 rounds in that 7 rounds the RAC does about 24 Pt's of damage and the Light AC/2 s do 28Pt's of damage .  Examine the slim tonnage difference and that same targeting computer could add another
2 ER-Med lasers to the mix. My take is neither Rotary or ultra is as good as the Light/AC with Precision ammo and a targeting computer as weight of RAC are high and the range bracket are a the same as the light . The ultra is not as good as a light AC either .  However when you go above the AC5 to 10 or 20s  I get better results with LBX Cannons or ultras with Targeting computers  or even standard AC with precision Rounds and targeting computers however the effectiveness VS tonnage gets worse.

[sebster]

Your point is taken ; however a RAC/2 averages about 6 pt / hit and say hits 1/2 the time . 3 light AC2 w targeting computer and precision ammo averages 4 and hits almost all the time

The light ac are 4 tons each for 12 tons total, before you account for the targeting computer. So the real comparison is 2 ac2 against a rotary ac2, giving both a targeting computer or neither. Range is identical so the only advantage to the light ac2 is precision ammo... and against that the rotary is averaging 3 hits to the light ac2 getting 2.

Ammo doesn't mean much because it's 45 shots a turn, 2 tons will last a match easy.

[Col Toda]

I just think accuracy even at 2 light AC/2 VS 1 RAC /2  has a little more utility as they do not jam; can use precision ammo ;
and goes through 1 ton of precision ammo in 11 Turns vs 9 turns for the RAC/2 at fire rate of 5 . A previous post had the idea of going thru all your ammo as a good thing ; it is : if you hit with most of it . Say over 9 Turns the RAC is like to hit 5 Times say 30 pts and the light AC / 2 is likely to hit 16 times for about 32 points and more importantly at further range before the enemy hits . Yes it is very little difference however one ton of ammo has more 2 turns of endurance and does not jam . You pay for it in Cost
of ammo Precision ammo Cost 6 X standard about 36pts/ ton VS the RAC of 30pts  20% more damage per ton . Expensive yes but hitting sooner while closing  and hitting later if they are moving to withdrawing is important those 2 extra turns of endurance make a difference if you can reliably hit them at long range both coming and going.  Military hardware has always paid a premium for even the smallest edge over the enemy and a 20% edge for about 600% cost in ammo is representative of this trend.

[Arkansas Warrior]

You're stacking the odds against the RAC, and overestimating the TC bonus.  -1 TH won't take you from "hits 1/2 the time" to "hits almost all the time", and you don't have to fire five RAC rounds all the time.  I increase ROF as TNs drop.  Only one or two shots at TNs of 9-10, but if I somehow end up with a TN of 2-3, let her rip full bore.

[CloaknDagger]

I just think accuracy even at 2 light AC/2 VS 1 RAC /2  has a little more utility as they do not jam; can use precision ammo ;
and goes through 1 ton of precision ammo in 11 Turns vs 9 turns for the RAC/2 at fire rate of 5 . A previous post had the idea of going thru all your ammo as a good thing ; it is : if you hit with most of it . Say over 9 Turns the RAC is like to hit 5 Times say 30 pts and the light AC / 2 is likely to hit 16 times for about 32 points and more importantly at further range before the enemy hits . Yes it is very little difference however one ton of ammo has more 2 turns of endurance and does not jam . You pay for it in Cost
of ammo Precision ammo Cost 6 X standard about 36pts/ ton VS the RAC of 30pts  20% more damage per ton . Expensive yes but hitting sooner while closing  and hitting later if they are moving to withdrawing is important those 2 extra turns of endurance make a difference if you can reliably hit them at long range both coming and going.  Military hardware has always paid a premium for even the smallest edge over the enemy and a 20% edge for about 600% cost in ammo is representative of this trend.

I don't know when we went from CRAC2 vs 3xCUAC2 to ISRAC2 vs 2xLAC2, but okay, I can still do that.

I actually would take 2xLAC2s over a single RAC2. Not because of precision ammo, but because of ALL the ammo. Flechette is nice against infantry. AP is nice against reflective armor. Precision is nice against everything. Flak is nice against VTOLs and Aeros.

LAC2s have much more versatility, and really that's what people use ACs for. That and the ease of repair and production.

You're stacking the odds against the RAC, and overestimating the TC bonus.  -1 TH won't take you from "hits 1/2 the time" to "hits almost all the time", and you don't have to fire five RAC rounds all the time.  I increase ROF as TNs drop.  Only one or two shots at TNs of 9-10, but if I somehow end up with a TN of 2-3, let her rip full bore.

It's actually -2 to hit with precision.

[Arkansas Warrior]

Even so, considering the bell curve nature of to-hit rolls, that could be as little as an ~8% increase, and I don't think it's ever going to be near 50%.  Though to be fair, there are times when a shot that would be impossible on RACs is possible on LAC2s+TC+precision.

[CloaknDagger]

Even so, considering the bell curve nature of to-hit rolls, that could be as little as an ~8% increase, and I don't think it's ever going to be near 50%.  Though to be fair, there are times when a shot that would be impossible on RACs is possible on LAC2s+TC+precision.

If your chance to hit is 1/11, that is, you need to roll 12 to hit, then -1 to hit is a 100% bonus, because it moves it from 1 possibility, 12, to two, 12 and 11.

If your chance to hit is 2/11, that is, you need to roll 12 or 11 to hit, then -1 to hit is a 50% bonus, because it moves it from 2 possibilities, 12 and 11, to three, 12, 11, and 10.

Also, it should be noted that tracer ammo gets you -1 to hit at night, pretty much for free.

Goes well with stealth armor.

[Arkansas Warrior]

If your chance to hit is 1/11, that is, you need to roll 12 to hit, then -1 to hit is a 100% bonus, because it moves it from 1 possibility, 12, to two, 12 and 11.

If your chance to hit is 2/11, that is, you need to roll 12 or 11 to hit, then -1 to hit is a 50% bonus, because it moves it from 2 possibilities, 12 and 11, to three, 12, 11, and 10.

Also, it should be noted that tracer ammo gets you -1 to hit at night, pretty much for free.

Goes well with stealth armor.

Yes, but the poster I was responding to said  "a RAC/2 averages about 6 pt / hit and say hits 1/2 the time . 3 light AC2 w targeting computer and precision ammo averages 4 and hits almost all the time"

That's not the case.


It should also be noted that precision only helps against a target generating a TMM (yes, most of them will be, but it's still a situational rather than absolute bonus).

[CloaknDagger]

Yes, but the poster I was responding to said  "a RAC/2 averages about 6 pt / hit and say hits 1/2 the time . 3 light AC2 w targeting computer and precision ammo averages 4 and hits almost all the time"

That's not the case.

Maybe. I'm not getting any deeper into the math than that.

It should also be noted that precision only helps against a target generating a TMM (yes, most of them will be, but it's still a situational rather than absolute bonus).

Yep. But if you're firing an AC2 against an assault mech, you can probably kill them with your courage alone.

[Paul]

If your chance to hit is 1/11, that is, you need to roll 12 to hit, then -1 to hit is a 100% bonus, because it moves it from 1 possibility, 12, to two, 12 and 11.

If your chance to hit is 2/11, that is, you need to roll 12 or 11 to hit, then -1 to hit is a 50% bonus, because it moves it from 2 possibilities, 12 and 11, to three, 12, 11, and 10.

2d6 probability doesn't work that way at all.

There are 36 different dice combinations possible with two 1D6 dice. To visualize this, imagine two dice, each with a different color. (Blue and red) To get, say, an 11, you have 2 options: Blue 6, Red5, or Blue 5, Red 6.
To get a 12, you must get Blue 6, Red 6. Nothing else works.
So, there's 1 combination that gives you a 12, two combinations that give you an 11.

Here's the whole list of possibilities:

2 - 1 Combination
3 - 2 Combinations
4 - 3 Combinations
5 - 4 Combinations
6 - 5 Combinations
7 - 6 Combinations
8 - 5 Combinations
9 - 4 Combinations
10 - 3 Combinations
11 - 2 Combinations
12 - 1 Combination

You'll note that's a curve; that's what's referred to as the bellcurve of rolling 2d6.

This also means that the effect of a -1 bonus changes based on where you are on that curve. Going from a TN of 8 to 7 means you're to hit goes from 41.6% to 58.3% chance to hit.
Going from 12 to 11 is a change from 2.8% to 8.3% chance to hit.

It's quite literally 3 times easier to hit, though the chances of success are still only 1 in 12.

Paul

[CloaknDagger]

I'll admit it, I derped.

[sebster]

I just think accuracy even at 2 light AC/2 VS 1 RAC /2  has a little more utility as they do not jam; can use precision ammo ;
and goes through 1 ton of precision ammo in 11 Turns vs 9 turns for the RAC/2 at fire rate of 5 .

Yes, and for those advantages you are accepting a 50% drop in effectiveness, with two hits vs three.  Which is a fairly nice trade-off with no clear winner, and both types being optimal in slightly different roles (the light ac-2 being ideal for a support unit hunting high speed, low armour enemy, while the rac-2 would be preferred for crit hunting on heavy and assault mechs where you'd happily accept a slightly higher tgt number in order to score 3 hits and an extra chance of sneaking a crit.

I mean, both are sub-optimal in those roles compared to lb autocannons, but, well, we're talking about ac2 here, in order to use them you have to accept its going to be sub-optimal.

You pay for it in Cost of ammo Precision ammo Cost 6 X standard about 36pts/ ton VS the RAC of 30pts  20% more damage per ton .

Cost is actually very misleading when it comes to comparing weapons, and really misleading when it comes to ammo.  This is because the cost of individual weapons is completely dwarfed by the cost of the mech that's carrying them - once you've paid for the fusion engine, internal, gyro and all the rest (and really mostly just the engine) then you're already looking at a few million c-bills.  The difference for pair of light ac2 or a rotary ac/2 (200,000 vs 175,000) is fairly close to irrelevant.  And the difference of 1,000 for standard ammo and 6,000 for precision is simply irrelevant.