One ‘fast call’ that often crops up is the decision of Krak vs Frag missiles when targeting MEQs. So here’s a question:

Lothar the Longfang stands atop a bastion with clear sight to a squad of chaos marines. He sees one in the open, with four comrades in cover. Should he use a krak on the one, or frag on the four? What if all 5 were in cover?

6th edition has introduced the concept of focus fire, whereby you can pick out individual models in the open, and has also reduced some of the standard sources of cover save (e.g. area terrain, and firing through enemy units). Both these changes affect the decision to go frag or krak vs armored targets.

Let’s take the simple stuff first, say Lothar fires a krak at the marine in the open – how does that pan out. With 3’s to hit, and 2’s to wound theres a 56% chance of killing the marine. What about the frag on the four? Well the scatter die is generally worse than all but the lowest BS values, so Lothar’s odds of hitting will likely drop (though this is quite dependent on the layout of the target models and any other nearby models that could be hit by a scatter). My previous analysis, puts BS4 scatter as about equivalent to BS3, so lets say 4+ to hit, 4+ to wound, and 3+ armor saves; and let’s say one blast marker can cover all four targets. This gets us an expected kill rate of less than 37% – worse than the krak. In fact, you’d need to cover about 7 marines before it was as effective as 1 krak shot (with no cover).

Of course, opponents are not always so obliging, and all your targets may be in cover. With 5+ cover that Krak missile drops to a 37% chance of a kill, and 4+ cover drops it to 28%. So how does the frag compare in these circumstances? A frag blast that covers 3 marines is roughly equivalent to 1 krak into 4+ cover. In 5+ cover you need about 5 marines covered to be worth your while.

So what’s the answer to our question? Well, with some dope in the open, Lothar should krak away rather than frag the four. But when it’s five in (say 5+) cover then it edges towards frag – but there’s something you should keep in mind:

They are roughly equivalent but there’s a key difference here – I’m using the ‘expected’ number of wounds to compare, but a krak can only kill 1 marine whereas the frag can kill multiple. The catch is: while the frag can kill more, your are also more likely to walk away with no kills at all. The concept here is volatility – if you need that one kill then the krak is more reliable even in situations where the average says they are equivalent. Sometimes though, you need to take the chance on getting multiple kills (e.g. to force a break test) and for that you need the frag.