In my game, I am using the errata weapons for my players. And we recently got our hands on Rites of Battle to play with vehicles

My confusion comes from the armor values on vehicles versus the damage output from errata weapons.

For example. I remember from the tabletop game that a bolter could (if you get really lucky) destroy a rhino when shooting it in the rear. But from what I'm reading in Rites of Battle, there's no way a bolter will do anything but plink off the armor. A heavy bolter also isn't going to scratch a Rhino. On average, even a lascannon hit isn't going to stop a Rhino in the first shot when it was overkill in the tabletop game.

I assume someone else has come across this before so I'm interested in learning learning how others handled this.

Thank you.

Tabletop is not reality. Too much abstraction to support the intended pace of the game.

I will say, as I say all the time when the topic of vehicles come up, even the newest rules for vehicles, specifically attacking them, are still lacking behind.

A tank of any size is not simply a whole slab-side of uniform armor. There will be, if not weakpoints, at least devices or things which simply cannot take the same amount of punishment as the armor itself. A periscope, pintle weapon mount, or radar dish for instance definately doesn't have the same armor as the main hull. Of course, these things are smaller than the main tank and wouldn't get +30 to hit. It just goes to show, there is still more room for improvement.

Well, none of it is reality, obviously. However, the errata stats are not to blame for their exceptional resilience. Bolters only lost 2 points of average damage, Heavy Bolters 4, and Lascannons lost 6. Even with non-errata stats, bolters are "only plinking away" without Kraken rounds, and though a Lascannon is likely to get the job done, it's only barely (put another way, the chances of pre-errata getting the job done are around 70%, post errata is around 40%). I firmly believe this is intentional. The reasons for this are twofold:

1) To make Vehicles scary set pieces, rather than them melting in the first round. If you drop a vehicle or 3 on the party, and one round later they're gone and now the group is using them as cover, it doesn't really feel very epic or climactic. If it can be brought down by a single member, it also mitigates the need for cooperation and coordination, which honestly doesn't do any favors at all to the growth of the tactics or the roleplaying possibilities for the group. If you can take it down with normal bolter fire, what incentive is there to have someone climb up on top of it, use feat of strength to rip off the hatch (or cut it open with their chainsword or whatever) and drop in a grenade to kill the crew inside?

2) To make it so that when players are in a vehicle, they don't feel like they're surrounded by paper when they're facing hordes. Adding in the bonus damage hordes receive can make even a smallish horde using a relatively weak weapon a credible danger to vehicles, so if you don't want the player's own vehicle to be destroyed in the first round (which let's face it, would suck and leave the players disheartened, and questioning why they even bothered), you need them to be able to withstand some major punishment.

The last thing to keep in mind is that every righteous fury result for vehicles (on an attack that deals any damage at all to them) deals a result of 1d5 on the crit chart, which means that they can be immobilized, incapacitated, and taken out of combat without having to necessarily wipe out every bit of their structural integrity.

Edit: I guess my whole point, that I neglected to properly convey, is that I don't recommend houseruling or adjusting this, until you've actually gone through several battles with vehicles (ideally in all contexts- players on foot vs vehicles, players in vehicles vs infantry, players in vehicles vs vehicles), and have seen the combat play out as it's currently designed and intended. If afterwards you find it's a bit too much, sure, you can always houserule away, and knock their armour down 5 or more points, or apply something where their armour drops by a certain value after the structural integrity is reduced to X% of the base, or whatever you need to have combat flow correctly, but I'd try it stock first, and see what you think.