Ugh...the Blood Angels books are famous for having a high body count on Blood Angels.
In the 3rd book they actually ask the Flesh Tearers (a chapter with only 3 or 4 companies worth of marinesbecause very high casualty rate due to battle doctrine and the black rage) and all other descendands to save the Blood Angels because of their heavy losses.

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Personally, I lean toward the following:

Type: Infantry
Move: 10cm, Save: 5+, CC: 6+  FF: 5+
Weapon:
-1BP, Ignore Cover

The underground shell is to weak to really rank a blast template, and the normal shell is a little too strong.  

Having powerful CC overlooks the fact that it's one guy and a gun.  The FF value is the same as the Whirlwind

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For comparisons:
All fire modi of the Thunderfire Cannon uses 4(!) 3" Blast templates. This covers more ground than a Whirlwinds 5" Blast template.
- The explosivie ammunition has the same Strength as a Multilaser (AP5+/AT6+ in Epic) but ignores the standard Ork and Imperial Guard armour saves while the Multi-laser only ignores the standard Orks saves.
- The scatter ammunition has the same Strength as the Whirlwinds standart missiles (but allows only power armoru equivalents and better it's save) but Ignores Cover.
- The tremor ammunition has the same Strength as a frag-missile (but allows all infantry armour saves) but produces a shockwave which turns the ground into difficult terrain (Disrupt in Epic effectively)

All have a range which is a good deal longer than the Whirlwind but shorter than a Battlecannon.

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The combined area of the Thunderfire's templates is about 28.2 square inches, while the Whirlwind's template covers 19.6 (about 70%).  Make of that what you will.

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2BP would definitely be excessive, but they clearly should be BP weapons, like the Quad Gun is, which is probably the closest equivalent.

I reckon there should be an OR in the weapon stats: 1BP Disrupt OR 1BP Ignore Cover. You'd have to choose one or the other modes and because of the way combined barrages and special abilities work you'd have to go all one way or the other if you wanted to take advantage of either. Fits within existing epic ways of doing things and matches W40k and the choice of fire types there.

The DeathKorps QuadLauncher has 2 x AP5+ shots and the Baran Thudd Gun 1 x AP5+/AT6+ shot.
But the difference to the DeathKorps QuadLauncher is, that the Thunderfire Cannon CAN hurt vehicles. So BP are justified and i like that you have to choose between 1BP Disrupt and 1BP Ignore Cover.

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Oops yes; I was muddling it up in my head with the Heavy Mortar. Could be either way, but prefer the BP option. It may be 60cm but it's direct only, just not that long effectively and different niche from the Whirlwind.

Oh yes  

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Personally, I'm against giving the Thunderfire two fire options.  Firstly, the Disrupt option is really, really weak, and ranking it as 1BP feels incredibly generous to it.  

Secondly, the Whirlwind had a stronger Disrupt option in its minefield template.  Could be an easy upgrade.

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Back on page 2 I proposed thıs;

Thunderfire Cannon;
Range - 60cm
Firepower - 2x AP4+ / AT6+     Ignores Cover or Disrupt (choose when firing)


The conversation swiftly turned to talk of Dreadnoughts, but I still kinda like this stat.

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Plus, lots of small blast templates without Barrage usually means you don't get an Epic blast template.  Witness the Thudd Gun.  And it's not an indirect weapon...

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Evil and Chaos' idea looks not inappropriate.

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Either version i'm fine with The non-BP version fits more with the DK Quad Launcher though.

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I am coming round to those stats. How many points? Unit upgrade only or allow whole formations of them? Are they meant to be rare old tech or commonly used in large numbers?