**Explanation of terms**
**3d6**
- Three six sided dice rolled together.

3d6+1P
- Three six sided dice rolled together with a "penalty die", making four six-sided dice in total. The highest or joint-highest result is then ignored. This mechanism does not appear in the published
*Crossfire* rules.

2.5d6
- Roll 2d6 as normal, counting fives and sixes as hits, then roll a third die, but on this third die only a 6 scores a hit. A good way to do this is to roll one die of a different colour, or an average die, which has one 5 on it, but no 6.

3d6+2P
- Roll five six-sided dice, and ignore the two highest or joint-highest results.

3d6(6)
- Roll three six-sided dice and count rolls of 6 as hits. When firing with a machine gun at troops in a bunker in
*Crossfire* such a roll might be made.

3d6+3d6+3d6
- Make three rolls, each of 3d6, such as when three rifle stands of the same platoon fire at enemy in the open, as a "firegroup".

This table does not take into account the chance of a Kill result (three hits or more). Therefore, the bigger die rolls, like 6d6 do not appear to as great as they really are. I wanted to compare like with like, and there are many situations in *Crossfire* when 2d6 is rolled, such as rifles firing at targets in cover, and these never have a chance to score a kill.

Above, we can see the effects of modifying 3d6 (the dice used for rifles firing at targets in the open) in five ways: -1 die (rolling 2d6 instead, such as at targets in cover); a penalty die (3d6+1P); -1 pip per die (3d6(6)); knocking off half a die (2.5d6); two penalty dice (3d6+2P). These can also be combined, such as knocking off a die and -1 pip per die (sixes needed), such as when firing at targets in a bunker.

Notice that the effects of these modifications are not the same on the chances of a pin as they are on the chances of a suppress. For example, the chance of a pin or worse with 3d6+1P is lower than the chance with 3d6(6), but the chance of a suppression or worse with 3d6+1P is higher than with 3d6(6). Because of these quirks, I decided that a mid-way figure between the Pin-or-worse figure and the Suppress-or-worse figure, would be a fair measure of the overall effectiveness of the various die rolls, in the context of a *Crossfire* game, since Pins and Suppressions are the commonest results of firing.

One question I wanted to sort out, was the effect of my rules modifications on the fire-power of typical firegroups. The *Crossfire* rules state that a typical firegroup is made up of three rifle stands, which each use 3d6. In my version of the game, instead of three stands, each representing a section or squad, making a platoon, I have one stand representing a light-machine gun team, plus one stand representing a rifle team, making up a section. Machine guns roll 4d6. I wanted to make sure that the firepower of 3d6 three times was about the same as of 4d6 plus 3d6. To my relief, they come out as identical (60.5%).

Now to see this information in a more visual form:

This shows the final (mid-way between Pin and Suppress) scores for 3d6, and the various ways of manipulating it. The colours correspond to the colours on the table above. The top row shows a surprisingly even distribution. Note that the difference between 3d6 and 2d6 is twice the difference between 2d6 and 3d6(6). The effect of a penalty die (3d6+1P) is about the same on 3d6 as -1 pip per die (3d6(6)). So, if you want some kind of cover to be better than a wooden building or some bushes (-1 die) but not as good as a bunker (-1 die and -1 pip per die), then either a penalty die or -1 pip per die is the way to do it, at least for 3d6 it is.

This shows all the final (mid) scores for all the dice calculated. You'd have to plot Pin and Suppress chances separately to see all the quirks. The Red numbers are the normal dice, which get closer together as they get higher. Between these are the half-dice. The effects of a penalty die are very similar as the effects of -1 pip per die for 2d6 and 3d6, but -1 pip is a harsher penalty than a penalty die for 4d6 and 5d6. An important difference between 3d6+2P and 2d6+1P, though they look similar on this chart, is that it is possible to get a kill result (three hits) with 3d6+2P, whereas it is impossible with 2d6+1P.

**METHOD**
You may be wondering how the above calculations were done. The formulae may surprise you with their complexity. Click HERE to see the method.