The Baden Firing trials represent British 15” APC & CPC Shells vs. German circa-WWI KC armor. Specifically, I am referring to the limit case of 15” APC vs 13.75” of KC -- the limit case is about 1550-fps at about 25-30-degree obliquity.
The Bayern and Baden were sister ships.
My point is that the armor on the Baden and how it performed during the British firing trials is basically identical to the German's KDOS estimate of how circa WWI German KC armor will perform vs. 15” APC. All I'm saying is that I don't think there is evidence within the Baden trials of substandard performance of this ships KC armor.
The BADEN trial´s do not show substandart KC performance. At all, the armour didn´t fail a lot with spalling and plugging except when hit close to the plate edges as was the case with the 15in APC striking the turret face. Note that the view angle of the picture omitts the fact that this penetration is subject to plate edge effects:
To further complicate things, the author of ADM either made a typo or a miscalculation for the netto impact obliquity. This is stated to be 18.4 deg but the involved horizontal and vertical angles are referenced there to be 11 and 12 deg, respectively. That makes for a netto impact obliquity of 16.22 deg, only.
The projectile penetrated completely with very low remaining velocity and received sufficiant projectile damage to render it blind (eventually it was blown up after many attempts with help of a guncotton charge to assess damage of a possible high order burst inside the turret). The same happened to the other 15in AP striking the 350mm barbette, which didn´t blinded but burst in holing the 350mm barbette armour. Nose & shoulder were found inside the barbette, striking it at correct 11 deg obliquity.
Without fuse action it must be assumed that this projectile would have completely penetrated in this condition.
Two more 15in APC tests were conducted at 30 deg (one at the CT and another on a barbette from the 2nd series of trials) and neither was able to penetrate or to hole 350mm KC at this obliquity, the round 15 from 1st series of trials hit the CT and APC round No.6 from 2nd series of trials hit the very joint of two 350mm plates of barbette A at 32 deg and made a dent 3in deep).
No 15in trial APC penetrated 350mm KC in a condition fit to burst.
One projectile hit the curved 350mm barbette at 11 deg and burst in holing (probably penetrated with a blind fuse)
One projectile hit and barely penetrated the 350mm turret face of B in blind condition close to the plate edge at 16.2 deg
At 30.1 & 32 deg these projectile couldn´t hole nor significantly damage 350mm (dented in by 3in on the plate joints).
The limit obliquity is probably in between 15 and 20 deg for the projectiles of these trials to defeat 350mm ww1 vintage KC at 1550 fps.
Striking in within 11 and 16.2 deg netto obliquity, it is highly unlikely that they could penetrate 0.918 cal ww1 vintage german KC in a condition fit to burst (Round 14). If the fuse remains intact, the delay would blow up these projectiles anyway before they completely pass the plate (Round 9). If they happen to strike at larger oliquities, they will fail to penetrate or significantly damage 350mm KC plates (Round 15 from series 1 and Round 6 from Series 2)
From evidence of the discussion of these results, it appears that MkIII GREENBOY were used for these APC impacts mentioned as the RN was statisfied with the armour piercing performance of their "new" APC. Alternatively, also MK1-mod may have been used in these trials (these were old Mk1 APC given a new armour piercing cap, copied from Krupp and remodeled nose with 1.6D headradius instead of the usual 2.0D of original Mk 1 to fit the new cap).