I'm talking about actual combat reports and accounts from books- not wiki'. I've never read of an account of shots bouncing off the P4's front.
The 80mm vertical was a very theoretical protection that was within the upper limits of the 76mm/75mm's performance. Special AP rounds were enough to go through it although conventional AP rounds were less certain.
I can´t completely follow this logic. Tungsten rounds which greatly improved performance in regard to armor penetration weren´t very common. M4 Shermans, even with the 76mm gun didn´t get them in the west until 1945. Those were reserved for the tank hunters.
Those rounds were also less accurate.
And those few rounds don´t make the enemy tank bad in every engagement. It would be saying that the IS-2 would be an easy kill always, because the tungsten round of the Panther could penetrate it at long range - though if we look at the reality there were almost no Pzgr. 40 available.
You say yourself that regular AP rounds were less certain to go through the Panzer IVs armor. Thus I think we both agree that the Panzer IV actually had the advantage of engagement range and protection until 1944.
The IV-H was very much a late war tank..within the last year of the war sort of business. T-34/85's, Shermans 76/Fireflies had proliferated greatly since then- the latter often encompassing half of tank platoons and the former being universally adopted by tank units.
I´m not comparing the Panzer IV to the later Shermans and T-34 here. I´m talking about the time from early 1943 - summer 1944, were Soviet tank losses increased drastically. This actually has to do with the upgun and increase of protection on the Panzer IV. Actually Shermans were mostly 75mm versions in Normandy. Allies were surprised to see an increasing number of Panthers and only by August there was an increasing number of 76mm armed Shermans available. The British meanwhile had the Firefly, but only 1 of 5 Shermans was this version. The Germans in the defensive role thus picked Fireflies out first.