[Mobhack]

Bunkers are already treated as not 100% proof - some effect from non-penetrating hits does "leak through" and kill defenders. But bunker crews are usually quite large...

With AP, it is best to manoeuvre till you get a shot at the weakest face - which is usually the firing slit at the front. AP has less HE kill effect, so if knocking on the sides He works best - try using e,g the SU-152 that has an all-HE load-out.

In MBT, bunkers are suicide machines from the time that 105mm APDS etc is common since the penetration scores of those over-match most field fortifications, though there are some "fortress" types with high defences. In MBT. If defending then about the only bunker type I look at is the ones with the 360 degree HMG as a good suppressor while they last and use those to protect a few with a Milan or similar, with TI vision. In WW2, the AT bunkers with a decent ATG are my go-to items, if thee is somewhere to plonk them with a good field of fire, and hopefully the enemy wont cover them with smoke (the simple counter till you get ones with TI in MBT).

The main advantage of bunkers though is that they do resist an artillery preparatory bombardment rather well, better than troops in trenches other than a fire trench/AT Ditch. So if your regular opponent likes to "mow the lawn" with a creeping barrage, they can be handy. But using the points on mines or dragons teeth is probably a better investment until those that can see through smoke arrive.

In WW2, a section of 2 Marders which will dig in, and can then move to react to the enemy (if the barrage does not do them in!) is maybe even better.