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RXBs vs RBT - Secrets revealed with maths! 
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Malekith's Best Friend
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RBT = Reaper Bolt Thrower
RXB = Repeater Crossbowmen
AS = Armour Save



OK, so i have always lived by the rule of thumb that "when using the RBT its better to use the 6 shot versus anything except when you can hit cavalry in the flank". And i have also used the rule that "RXB will do more damage (point for point) than RBT assuming you are within 24 inches".

I have now done the ridiculous amounts of calculations needed, not only to check these "rules", but also to check when its best to use single shot with the RBT, including rank piercing.




I did NOT calculate for the following:

#Rank piercing for multi wounded creatures (since its incredibly unlikely to happen)

#Ward saves for rank piercing (a unit with ward save or regen save will be MUCH more resistant to rank piercing. If a unit has ward/regen, dont try to pierce its ranks. wards will not affect any other part of the calculations though, dont worry)




I will not print out the exact numbers, to spare my already tired fingers, but i will give you an idea of when to use what type of shot. If you dare trust my maths (i have a MSc degree) you can use these facts for great benefit. If you dont trust me, you can redo the calculations yourself :twisted:

I am assuming 1 RBT compared to 10 RXB. I am assuming you are at between 12 and 24 inches. The RBX will hence have an edge at closer range, and the RBT will have the edge at longer range, but most shots in the game are fired at this distance.

The results are shown in the table below:
Image
* = Use single shot only if the target has at least 3 ranks to penetrate.



So, i hope this will help some of you to make the choice between RBT and RXB, and perhaps more importantly, choose between 1 and 6 shots with the RBT.





ps. If some one thinks this is Draich-worthy, feel free to link it in there :P

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Last edited by Lord tsunami on Sun Apr 10, 2011 3:05 pm, edited 1 time in total.



Sat Apr 09, 2011 10:49 am
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Executioner
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Awesome. I would LOVE to see your maths.

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Sat Apr 09, 2011 11:04 am
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Thank you for the data.

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Sat Apr 09, 2011 12:18 pm
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Malekith's Best Friend
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Quote:
I would LOVE to see your maths.


i have an excel sheet i designed to easily calculate the number of kills when you put in the number of attacks, the "to hit" required and so on. I simply calculated the number of kills for RXB/6-shot/single shot for every single value of toughness and AS. The rank piercing is a little trickier, but i made it work. basically if 1 shot at the first rank scores for example 0.5 wounds, you simply add 0.5 attacks that always hits to the second rank and so on (modifying strength as you go). generally speaking the contribution of rank piercing after the third rank is insignificant.

And no, i wont upload my sheet. its not totally intuitive to use, and im not gonna write tonnes of instructions for it. neither will i have ppl who dont understand the maths use my tool to prove this or that. If you know how statistics work, you can easily make a sheet like mine yourself, and then i wont be to blame if you use it wrong. If you dont know enough statistics to make such a sheet, i suggest you take me on my word, and not try to do calculations of your own. Also you could ask a friend who knows more maths to explain it to you. Statistics+Warhammer = FUN! :D

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Sat Apr 09, 2011 2:51 pm
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Lord Tsunami wrote:
i have an excel sheet i designed


That's how I roll. I'd be interested to see if the chart changes when the RXBs moved.

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Sat Apr 09, 2011 2:58 pm
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Basically the differences are small enough, that if the RXB move, they will automatically be worse than the alternative, and if they fire at close range they will be better than the alternative.

Probably thats not true in some of the most extreme cases (very high or very low T, or very high AS) but it should be a good enough estimate. best to do the calculations yourself when you know what specific case you want to look at ;)

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Sat Apr 09, 2011 4:05 pm
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Very nice. I actually assumed something close to your table, so its good to see that I was right.

I think buffing the RXB with magic will be more advantageous than buffing the RBT. So I will stick with running mostly RBT and just add a single RBT occasionally.

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Sat Apr 09, 2011 7:39 pm
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I think he meant mostly RXB ^.^

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Sun Apr 10, 2011 1:17 am
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This is interesting, thank you for your efforts. I just have a couple of questions:
- Did you use -2 armor reduction for RBT or -3?
- I'm sure your calculations are correct, but can someone explain the rationale behind the "6-shot is better against enemies with low armor if and and only if they have T5"?


Fri Dec 14, 2012 1:31 pm
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Why would he use -3 for the RBT? That would be illegal, as RBTs have a -2 armour penetration.

6 shot would be best against enemies with T5 because then they would be wounding on 5s while RxBs would be wounding on 6s, meaning that only half the total number of RxB hits would wound compared to RBT hits. Against T6 or above enemies they would both wound on 6s (so no difference in the % of hits that would successfully wound), and against T4 it would be RxBs wounding on 5s and RBTs wounding on 4s, which would mean only a 16.666% bump in the number of wounds that hits made by the RBT would get over the RxBs, which would be more than adequately offset by the much greater number of hits that the RxBs would make.

Or so I would imagine ;)

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Fri Dec 14, 2012 2:01 pm
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what red said ^^

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Tue Dec 18, 2012 6:59 am
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