Preliminary British intelligence on the Tiger that was available for fairly general consumption throughout 1943 did not set up great expectations for the quality of its armour, already indicating that it was prone to spalling and cracking. Trials conducted in October confirmed these suspicions. The following are excerpts from WO 194/744, "Firing trials in Tunisia against the hull of a Pz.Kw.VI" made available to me by Alexander Sotnikov. I'm not going to copy the whole report, but there is a pretty good example that shows how greatly variable the quality of German armour has become even by 1943. For your convenience, a penetration table for the 6-pounder gun is attached.
The first attack is on the right side of the hull. British AP is expected to penetrate 80 mm of armour at around 1900 f/s, so the performance is about on par with British MQ armour. The large flakes that are dislodged under 6-pounder attack are pretty damning, however.
6-pounder attack against the left side yields significantly better results. The ballistic limit is more than 200 f/s lower, with larger flakes breaking off. 1700 f/s is equal to about 65 mm of British MQ armour.
The conclusions in the report are not surprising. The increased hardness of the German armour offers little in terms of additional protection, and it is found to be much more liable to fail when attacked than British armour. When one's enemy describes one's progress as "distinctly encouraging", that should be quite a cause for concern.
