So...numbers can be funny sometimes. We all know meltas are teh uber tank rapers in the current rule set.
But, there are other weapons out there that do things meltas dont, and Ive been toying with them. I saw a post in which someone said they thought Assault cannons were better Vs av 14 than las cannons. I think most initial reactions will be 'Bullshit!' Mine was.
But, then I crunched the numbers with the nifty Vassal40k- this is 100,000 rounds worth of fire for each weapon- hittin on a 3+ (PS- crunchin the numbers for 400,000 ac shots made my laptop use its safeword)
So Lascannon vs AV 14 11056 dice glance (5), 11186 dice penetrate (6+)
Metla-with 2d6 vs Av 14= 9074 dice glance (6), 38830 dice penetrate (7+) =
Melta w/1d6 vs Av 14= 11071 dice glance (6) =
Assault Cannon vs AV 14 14786 dice glance (8), 15082 dice penetrate (9+)
Lascannon Vs AV 13= 11036 dice glance (4), 22466 dice penetrate (5+)
Melta w/2d6 vs av 13=7274 dice glance (5), 48219 dice penetrate (6+) =
Melta w/1d6 vs Av 13= 11085 dice glance (5), 11089 dice penetrate (6+) =
Assault Cannon vs Av 13 = 14288 dice glance (7), 29664 dice penetrate (8+)
Lascannon Vs Av 12 = 11097 dice glance (3), 33222 dice penetrate (4+) =
Melta w/2d6 vs av 12=5496 dice glance (4), 55943 dice penetrate (5+) =
Melta w/1d6 vs Av 12= 11042 dice glance (4), 22196 dice penetrate (5+) =
Assault cannon vs AV 12 = 45188 dice penetrate (7+) (note- cant glance AV 12 since a 6 pen roll adds the 1-3 to its AP)
Lascannon Vs Av 11 = 11019 dice glance (2), 44327 dice penetrate (3+) =
Melta w/2d6 vs av 11=3655 dice glance (3), 60849 dice penetrate (4+) =
Melta w/1d6 vs Av 11= 11207 dice glance (3), 33192 dice penetrate (4+) =
Assault cannon vs AV 11 = 44201 dice glance (5), 44956 dice penetrate (6+)
Lascannon Vs Av 10 = 11007 dice glance (1), 55415 dice penetrate (2+) =
Melta w/2d6 vs av 10= 1902 dice glance (2), 64722 dice penetrate (3+) =
Melta w/1d6 vs Av 10= 11067 dice glance (2), 44509 dice penetrate (3+) =
Assault cannon vs AV 10= 45276 dice glance (4), 89708 dice penetrate (5+) =
So, Meltas within 12/6" are king Vs Heavy armor. Assault cannon are however capable of more penetrating hits than Lascannon. But the Lascannon has the edge over Meltas when they are only using a single penetration dice.
Once you get to lighter armor however, the sheer number of Pen & glancing hits the assault cannon puts forth is pretty impressive. This seems to make it an ideal weapon for working over squadron based vehicles.
And, all this isnt even getting into using the weapon Vs Infantry.
All this being said- I really think the Assault cannon- while 'nerfed' from 4th ed, is still worth the points in 5th ed.
This also has me wondering if the Assault cannon is better than the Cyclone/Typhoon, as for anti vehicle use krak missles are very easy to compare (use the melta w/1d6 stat line and jsut x2 for the results- its rough but close enough), however, 2 frag missles are pretty random, so are really hard to balance in an anti- infantry role. Oddly, it looks like the Assualt cannon is better Vs Av 14, and AV 10, but a Cyclone/typhoon would be noticably better Vs 11,12, and debatable vs 13 if you look at the glances. So, I think for termies, the assault cannon is better- as it cooperates with their 24" storm bolter range. For speeders, the typhoon gives better stand off range.
Note: I realize this is pure meta-gaming- there are numerous factors unaccounted for.