The 88mm Flak 36 is the same gun as the Tiger I mounts. Same caliber length (L/56), tiger I just has a muzzle break.
AP rounds should be the same.
Something I think is really neat about the 88's AA round is that if you fuze it correctly, you can get an airburst. Would be great for taking out troops, even if you can't see the map room bunker over the bushes, you might be able to get an air burst over top of the map room.