Author Topic: Custom D20 hit location dice  (Read 4850 times)


  • Master Sergeant
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Custom D20 hit location dice
« on: 05 July 2016, 21:45:23 »
Bottom Line Up Front:  I made custom D20 hit location dice to speed up the game.  Read on if interested…


The game takes too long to play and has too many look-up tables.  I love the nuance and complexity of the game, but as a complete whole it can be daunting to play, especially for new players.  I want to streamline and speed up play, but not simplify the game to the level of Alpha Strike (which there’s no need for me to try to recreate anyway, since it already exists).


Rolling a lot of dice takes a long time, especially location rolls for the larger cluster weapons.  What I attempted to do was to find an elegant solution that would satisfy the following requirements, in order of importance:

1.   Maintain the chance to roll physical dice;
2.   Speed up the game without sacrificing complexity; and
3.   Maintain hit location ratios as true as possible to the original game.


I determined that a “Box of Death” approach wasn’t satisfying to me, so I looked for another way to speed up location rolls.  I created a [custom Excel spreadsheet], which worked great, but again wasn’t as satisfying as rolling physical dice. Rolling multiple sets at once of different coloured dice was an option, but then you still need to match the dice together and look up those numbers on a table, so no real time savings there.

I sat down with Excel and did a bunch of calculations, finally deciding on D20s as the way to go.  (Had I found this reasearch sooner, I could’ve saved myself a bunch of time :P)  I ordered some blank D20s and wrote on each face, creating a set of Mech dice (white) and a set of Vehicle/VTOL dice (ivory), 10 each.  Sorry, no love for Protos here, at least not yet.  Changing the hit tables to a D20 system could also work with normal, numbered dice (and obviously has already been done), but then you would still need a table to look up what location each number represents, and we’d be no further ahead than when we started.

The Excel sheet with all the math is attached, for anyone interested.  Personally I love that stuff, but I won’t bore you with it here.  Somewhat surprisingly (to me, at least), the probability numbers actually work out quite well.  I also took care to space out similar hit locations on the die as best I could, trying to mirror how a regular D20 will have opposite numbers (high and low) in opposite positions.

Part I: Mechs

When a Mech gets hit from the front or back, the locations are self-explanatory.  The part that might seem confusing at first glance is the different colours, which come into play when rolling hits from the sides.  In that case, anything in blue counts as the body part written, but on the close side, rather than the side printed.  The one oddity is the “LT” location where only the “L” is in blue (you can see it on the die roughly in the center of the picture).  For that one, if you’re rolling from the side, rather than hitting a Torso, the shot hits the close Leg.  I’m not happy about doing it this way, but it turned out to be the best way (really the only way) to make the numbers come out right.

In these examples a Mech is taking incoming fire from the Right Side:

Location die reads:     Colour:Damage is taken on:
LTRedLeft Torso
LTBlueRight Torso
LTBlue L, Red T     Right Leg

If you roll the Crit location (represented on my dice by the red crosshair symbol), roll 1D6: on a roll of 1-3 the shot scores a TAC, 4-6 the shot hits the Head.  If you are using floating crits and on the re-roll you get another result of Crit on the location die, roll 1D6 in the same way to determine if the location is the Head or the appropriate torso.

Probabilities: Other than the Far Arm when hitting a Mech from the side, no location, on any roll, changes more than 10% relative to its original probability.  All things considered, those are numbers I’m comfortable with.

Part II: Vehicles & VTOLs

The locations labelled “(F)” are critical hits only when taking fire from a side arc.  If you roll a location with a “+” added to it you also roll for a motive critical hit.  As it was with the Mech dice, some of the locations are in red, while some are in blue.  The colours on these dice, however, signify the difference between vehicles and VTOLs.  All vehicles use the hit locations as written, while VTOLs ignore the motive hit symbols and treat any location in blue as a Rotor hit. 

If you roll the Crit location, roll 1D6: on a roll of 1-3 the shot hits the Front, 4-6 the shot hits the Turret/Rotor.  The one potentially tricky part here is that the locations labelled as front (“F”), left (“L”), and right (“R”) orient according to the direction of incoming fire.  To put it another way, “F” means the location directly facing the incoming fire, “R” and “L” mean one facing to the right or left, respectively.  The “one facing right or left” can mean either according to the player making the rolls, or the player marking the record sheet.  As long as the players agree it really doesn’t matter, but personally I like to call it according to the defending player, as then the rolling player can just call out the results and the player marking the sheet just interprets “one facing right” as “one facing right” on their sheet, no tricky 3D mind-rotating necessary. 

As for the math, it’s similar to the Mech dice; no location, on any roll, changes more than 10% relative to its original probability.


This system really cuts down on the number of separate rolls required in a game and all but eliminates location table lookups, thereby cutting down on game length and turn complication. 

I have played a few games with these dice now, and so far I really like the results.  My preferred method (for non-cluster weapons) is to throw 2D6 and the D20 together, checking first to see if you hit and then reading the D20 to see where, with no requirement for additional rolls or charts.  For cluster weapons, no matter how many clusters hit, you only need to roll once.  (Okay, so an LBX-20 may need more rolls, since I only have 10 location dice for now.)

So does it meet my criteria?  Let’s see:

1.   Maintain the chance to roll physical dice: Yes
2.   Speed up the game without sacrificing complexity: This definitely speeds up the game, and all the right complexities are still there.
3.   Maintain hit location ratios as true as possible to the original game: This one is up for debate; personally I’m very comfortable with the numbers.  There is only one location, across all Mech/Veh/VTOL rolling scenarios, where the probability changes more that 10% relative to the original tables.  Given the amount of time this can save, I’d say that’s an acceptable loss.

Thanks for reading, if anybody made it through all that.  Comments and questions welcome!


  • Master Sergeant
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    • ScrapYardArmory
Re: Custom D20 hit location dice
« Reply #1 on: 06 July 2016, 07:49:20 »
Very well thought out and executed idea.  And bonus points for providing a picture of a finished piece.

I've thought about such things too.  In my case, I always wondered if there was a way to combine dice to naturally emulate the cluster hit table.  Something akin to roll a set of custom 3D6 and add up the values to get the cluster hit number.

I never was able to find a way to get close due to the penchant for BT to use odd and even numbers in unusual ratios.

Well done idea.


  • Master Sergeant
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Re: Custom D20 hit location dice
« Reply #2 on: 06 July 2016, 14:46:01 »
Thanks!  I too feel challenged to do something with the cluster table, although so far all I've been able to do is tweak the numbers a bit to make the math look better, as many have already.  At this point I still haven't found a simple yet accurate solution that doesn't violate the cardinal rule of "don't create more problems than you fix".