You mean the max damage a LMG can roll is 8.. .2 for base damage and 1 for each Ammo dice.. so potentially 8.. very very unlikely as you stated though.. But yeah, we will see whats coming.
I actually miscalculated, sorry, the max damage for an LMG is 5: Weapon damage 2 + 1 for each extra stunt = 5. Ammo dice hits counts as separate bullets.
Ok so in this example. Your first bullet does 5 damage? and each subsequent hit from the ammo dice does 1 damage? So only the first would penetrate? This makes a lot of sense now. If you look at some of the bigger MGs I think you might still run into this issue. (DSzKM HMG could penetrate a tank)
The hit from the base dice in my can do max do 5 damage. The ammo dice can only cause weapon damage (2 for an LMG). My miscalculated example a couple of post above is a valid example for a GPMP (and with higher % if using an HMG). But still you need to be very lucky, and all my examples assumes that you have A A with you are shooting, something that is unlikely. For it to be possible, you probably must be within short range and stationary (and in the right angle) and still, the damage is not explosive so it can damage something inside with a point or so, but that's it. Then the tank will return the fire and he doesn't need to be super lucky to hit and he will most likely do more than token damage.
But, hey who knows. The stats may change before this alpha-period is over and if it doesn't change then I can live with it (if my players want to be heroically cinematic, I welcome them).