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I like to work from basic stats when picking units and weapons in my army, and playing IG, that means trying to figure out alot of large and small blasts and such.
So, how exactly can you make an educated guess on what effect a given template weapon will have?

My 2 biggest issues are scatter accuracy and # of models per hit. Given scatter, what's the "statistical" average of models you can expect to hit with a given shot? Better yet how do you even figure out a statistical average of models on a direct hit? Telling me that the large blast template can fit X models under it at maximum is kind of useless when I will never get to fire a shot against a unit positioned like that on the table.

I know from anecdotal experience that my flamers average about 6 models per shot, my small blast weapons about 3 and large blasts maybe 5, which I use to make my guesses, but that hardly seems sufficient to come up with reliable numbers.

So, has the "mathhammer" been done on these problems?

Well right off the bat you have a 1/3 chance of scoring a direct hit with a blast weapon, which is true for most conventional blast weapons.

You also have to consider various factors, such as how well your opponent has spread out, what weapon youre firing.

There is no "golden answer". You have to assess it on a case-by-case basis.

Actually playing the game, helps, too.

SoloFalcon1138 wrote:Actually playing the game, helps, too.

Wow there, don't go rocking the boat with crazy suggestions like that!

thanks for the great responses. Both of you have alot of keen insights to provide to this discussion clearly.

First you need to calculate the to hit. This is different for blast markers and templates.

Some stuff to know:

The Blast marker and the Large Blast marker are 3" and 5" diameter, respectively.

Small bases are 25mm or ~1 in diameter. Larger bases are 40mm, or ~1&1/2". The large 60mm bases are ~2&1/3".

Blast markers scatter 2D6-BS. A BS3 unit will therefore hit on both rolls of "Hit" on the scatter dice, and rolls of 2 and 3.

Spacing is a tricky issue. Players can't always manage ideal spacing due to stuff like the Lash of Submission, tank shock, terrain, and so on. But wide spacing can work well for the shooting player. Closely spaced units are more likely to be missed entirely, whereas widely spaced units often give up at least one hit regardless of scatter.

Against a widely spaced unit, it can be handy to roll a 4 or 5 with BS3 so that the edges of the marker can clip two or more models, rather than being centered on a single model and only hit that one.

Roll a 6 and the marker is flipped over in the direction of the scatter.

So think about it: If you are shooting at a unit that is 9" wide with a blast marker, you want to aim for the model in the middle of the unit if you want to increase the reliability of hitting a model, rather than going for the thickest concentration and try to maximize potential. This applies to shooting at vehicles too, and moreso because you're only going to get one hit (unless firing into a parking lot, in which case aim to clip if you can glance or penetrate on a clip).

Templates are different. The template is ~8" long and ~2" wide at its widest. Ideally you want to be about 3"-4" away from a unit, and perhaps closer. Against a fully spaced unit with 25mm bases you should see three hits. You can often get more.

The Average scattering distance for a Blast Template in the Guard army is 4 inches, 3 if you have Pask on the tank (average roll on 2D6 = 7, 7 - 3 = 4. For Pask, it's 7 - 4 = 3).

For the Small Blast template weapons (such as Plasma cannons and Frag Missiles) aim at closely packed units. Units which are 1-2 inches apart will rarely get more than 2 or 3 hits. Against with large bases, dont even attempt to use the small blast template on anything but tightly packed units, as the size of the base would ensure that you only ever get one hit (so in the case of the frag missile, you'd be better off using the penetrative power of the krak missile). While you could argue that a small blast template has a chance to hit something, Models with larger bases tend to also be more survivable (either due to Armor, Toughness, wounds, or any combination thereof). The Plasma cannon can be used with marginally more success, but there are usually better targets.

Large Blast Templates can usually score 5-7 hits easily, even if the enemy spaces their models apart. Hitting packed models are even better, as even with a 4 inch deviation, it's not going to move that much from it's original target.

Note that all Blast weapons are not good against MCs, and only high strength ones should be used on multi-wound models, as no matter how many models you cover, each model only ever suffer one wound (take shooting 3 Ogryns with Lasguns rapid firing. There's a potential 20 wounds to be inflicted there, which on a good dice roll can obliterate the unit entirely, as it only has 9 wounds in total. With a battle cannon though, you can only ever do 3 wounds, as there's only 3 models and none of them are susceptable to a Battle Cannon's instant death).

Also, I should also point out that Barrage Weapons have a different way of using them, which will cause more devastation depending on the dice roll. Due to the Multiple Barrage rule, you only move the markers once. On a good roll, this can land you smack in the middle of the enemy troops. Consecutive "hits" would let you place the following markers anywhere touching the first one. In this sense, you should always take into consideration where the other potential markers can go when firing Multiple Barrages. A "Hit" at any point in this process can also save a failed shot, as either you hit your original target, or you can manually put the subsequent markers over enemy models. Barrage weapons also give cover saves based on where the center of the marker is, not where you fired it from. This can potentially deny the opponent a cover save, whereas a conventional Blast Weapon with a High strength will be negated by the same cover save.

Average scattering distance is faintly misleading if you're discussing the expected value of possible results. Results of 7 only happen 6/36 times. 6 and 8 happen 5/36 times each, 5 and 9 happen 4/36 times each, 4 and 10 happen 3/36 times each, 3 and 11 happen 2/36 times each, while 2 and 12 happen 1/36 times each. Non-7 results therefore happen lower 15/36, or 2.5x the average. You're more likely to miss big if you rely on targeting a clump of models rather than the geographical centre of the unit.

Targeting a clump has a higher chance of hitting more models on average actually. With over 50% of the scattering being 4 inches or less, and 1/3 chance of landing a "Hit" on the Scatter dice, you are much more likely to hit your initial targer rather than try and prevent the template from hitting nothing at all. Given that 6/36 of the dice results will mean no scattering whatsoever, it effectively increases the "hit" chance to 50% overall. Plus, on a scatter, there's only a 25% chance that it will be beyond the "average" of a 4 inch deviation, meaning such theoretical calulations are reliable. Plus who clumps their models together on the edge of a unit and spaces the other models in the unit out? A clump would be the geographical center of the unit.

Bruteboss wrote:thanks for the great responses. Both of you have alot of keen insights to provide to this discussion clearly.

lol



Unfortunately, excluding the average scatter distance (which doesn't provide much insight), there is no way to get a true average. If you were wanting to gauge the effectiveness of blasts there are simply to many variables--the most predominant being the way YOU play them--to do it mathmatically. The most effective way will be to proxy, and test in multiple games.

As stated in posts above, there are some useful rules of thumb. Don't waste shots on single units if aviodable. Don't waste shots on vehicles, if aviodable. Those annoying unit's that are evenly distributed 1-2" apart are always the best bet for a 3" blast.

From my personal playstyle, with BS 4, 2 models for a 3" is a mean average. 3 models with a 5" is a mean average.

Of course, having even one Plasma cannon on the field prevents your opponent from clumping units, and provides you with some control over his/her deployment.

[snipped]

I can make a diagram for both type of blasts based on BS if you want.