The Deathwatch Living Errata, version 1-1 shows Melta Bombs now only costing 12 req and having a Blast (5). The req I can believe, but the Blast (5) seems to be an error.

I want to give my players the discount on the melta bomb based not he Errata, but the addition of Blast is bringing into doubt the entire stat block.

Nevermind, I was missing the second entry for Melta Bombs in the Rites of Battle. I was also unclear that Blast (5) only meant the blast is 5 meters...though that still seems very high for a Melta Bomb.

Blast is only super relevant when the explosion is right on top of a solo (can they move out of the radius to dodge or not) or with Hordes (determines the number of hits). Why does a 5m explosion seem unreasonable for the ultimate demolition charge? Presumably part of the block is to make it not completely suck as a trap vs. Hordes.

If I recall correctly the TT Melta Bombs don't have much of a radius, so I can see where the question comes from. I can also see thinking it odd the melta has the same radius explosion as a frag missle.

Either way, I've had no problems with the melta bomb in the RPG to date due to the blast- my team uses them to great effect as a placed explosives and breaching tools. They don't use them on hordes, jury rigging frag grenades and the like is more economical (though I also don't tend to use hordes with body armor and toughness high enough to warrant a melta), but they use them on vehicles, doors, etc.

Melta bombs are essentially shaped charges. Except the shaped Jet penetrator is actually super-heated melta stream. They don't blow "up" as much as blow "in a single direction".

In most fluff the actual explosion from a melta bomb is miniscule, with the exception of the targeted area. With the melta stream cutting into, and then through the targeted area.

So if you're using it to blow open a door you'd put it over the latch or hinges, not over the middle of the door (unless theres a locking mechanism there like a safe). The Melta would cut through the door destroying the latch or hinges allowing you to open or break down the door. If you put it over the center of a typical door, you'd simply blast a whole about, I don't know, 6-12" accross in the middle of it. I guess that 'could' work IF there was some way to reach the locking mechanism on the other side, but other explosives could just as easily put a simple hole in a door (you're doors may vary, armoured hatches can be very strong).