A question regarding ww2 bunker busting!

[Bushbaby]

I would like to know what kind of tank/ direct fire ammunition and caliber that was needed to knock out:

a) a concrete pillbox.

b) a trench or similar dirt/logs entrenchment.

Did you use HE or AP? What caliber? Where did you need to hit (especially regarding a trench that has no real silhouette)?

I hope some of you experts here can help me shed some light on these questions?

[Ballardian]

 I guess it depends, most nations reasoned they'd need some sort of 'bunker busting' gun or ammo & built accordingly - but these weren't usually on your main fighting tank but mounted on some variety of SPG or Assault Gun (or, at its extreme, leading to building railway guns). If the target proved beyond the capability of the vehicles standard HE or AP round, the fortification would likely have been bypassed & dealt with by some combination of aerial bombing or artillery (& at the beginning of the war this wold have been fairly likely, given the comparitive weakness of early tank guns).
   The StuH 42 is a good example, the proven 105mm LeFH would've been ideal, though the same (or similar weapon) ended up on numerous other vehicles (Grille, Wespe etc). The Brits built with the idea in mind & produced the AVRE Churchill with a 290mm spigot mortar (the 'Flying Dustbin') & A39 Tortoise with a 32pdr in a fixed casement which was supposed to deal with the fortifications of the West Wall (but turned out not to be needed).
 So apologies for the round-about way of saying it:

  Pillboxes - generally an AP round - but depending on the caliber it could have been HE (if the gun/charge in the round big enough - see AVRE Churchill).

  Trenches - generally HE - if fused for airburst (& the gunner a good shot) especially effective - otherwise a ballistic trajectory (like that of a mortar) was better, but usually a tank would hose the trench with MG fire & use HE to suppress the occupiers (the Germans for instance told their crews in early 43 not to bother shooting at emplaced infantry or guns with the 50mm in the Pz III, but to have their Panzergrenadiers attack with far more effective motar fire).

[MartinR]

Earth/log bunkers don't respond too well to direct hits from 75mm HE on the embrasure, sometimes AP was used to blow a hole or three first. Even 37m worked OK for that in Burma.

Proper concrete bunkers are another matter. AP and HE at the firing slots from within 250m can be effective, but more generally you need some sort of demolition gun to actually blow a big hole in it.

[Etranger]

Earth/log bunkers don't respond too well to direct hits from 75mm HE on the embrasure, sometimes AP was used to blow a hole or three first. Even 37m worked OK for that in Burma.

Proper concrete bunkers are another matter. AP and HE at the firing slots from within 250m can be effective, but more generally you need some sort of demolition gun to actually blow a big hole in it.

A big enough gun firing AP or HE at the apertures will strongly 'discourage' the occupants however, viz the BuflaK in 1940 (designed as a bunker buster from the start), the M12 in 1944-45 & the 203mm howitzers in Berlin etc. (all pix c/o the internet)

[fred]

On D-Day the allies used normal Shermans against bunkers - but from very close range, so that they could hit around or even into the embrasures. This certainly upset the defenders inside the bunker, but had fairly little structural impact on the bunkers.

If you can suppress the defenders in the bunker (or trench) with fire from tanks or SPGs then your own infantry can get close to deal with the defenders.

[carlos marighela]

A small enough gun will also do the trick. The Australian Army tackled quite sophisticated earthen bunkers* and the odd concrete version using the 2pdr AP shot of the Matilda tank all through to the war's end 1945.


* Some of which were arguably better fortifications than their concrete equivalents, being constructed from a combination of earth or sometimes concrete filled steel drums, multiple layers of palm trunks and packed earth.

[Plynkes]

At Longues-sur-Mer they used HMS Ajax and Argonaut. Not an entirely efficient method, I'll grant, especially as one of the four German naval guns in those bunkers is still sitting in its mounting as I type this.

[Cubs]

A small enough gun will also do the trick. The Australian Army tackled quite sophisticated earthen bunkers* and the odd concrete version using the 2pdr AP shot of the Matilda tank all through to the war's end 1945.

Not to mention the superb Matilda Frog flamethrower tank!

[carlos marighela]

At Longues-sur-Mer they used HMS Ajax and Argonaut. Not an entirely efficient method, I'll grant, especially as one of the four German naval guns in those bunkers is still sitting in its mounting as I type this.

I strongly suspect that the survivors were candidates for hearing aids and clean trousers though. Of course that's presuming they weren't already part of some German elite, static, ear nose and throat battalion or stomach, kidney and haemorrhoid regiment.

[Just a few orcs]

Reading "D-day through German eyes Volume 1 and 2" In Normandy bombs containing powdered white Phosphorous were often used . the powder blew in through the slits and ignited.  Often dropped by fighter bombers coming in low to try and skim the bomb into the front of the bunker

[Rich H]

One of the Centaurs on the beaches of Normandy expended all it's 95mm ammo on a bunker without effect.

[Bushbaby]

Thank you! Your answers have been most helpful!

[Rich H]

British solution to the Westwall


US solution

[Mick_in_Switzerland]

Dear Rich,

They look fantastic.
Pleadse can you explain what they are and how big the guns are?
I think the top one is a Tortoise but I know very little about these weapons.

Thanks

Mick

[Rich H]

Top one is indeed a Tortoise, it's got a 32pdr high veolcity gun
https://en.wikipedia.org/wiki/Tortoise_heavy_assault_tank
https://en.wikipedia.org/wiki/Ordnance_QF_32-pounder

The lower one is the T-28 Super Heavy Tank Also known as the T-95 Motor Gun Carriage it has a 105mm high velocity gun.
https://en.wikipedia.org/wiki/T28_Super_Heavy_Tank
https://en.wikipedia.org/wiki/105_mm_gun_T5E1

The idea of both was to be able to take on the Westwall directly with enough armour to take hits from 88s
The war ended before either saw combat thought the T-28 was trialled for deployment in Korea


I mastered the 1/56 versions for Die Waffenkammer and the Tortoise is rather nicely painted by Jacob Lots