Bazookas used a shaped charge, if I remember correctly there was an inverted cone of copper in front of the explosive. On contact the explosive turned the copper into a plasma, which makes that hole.
(I probably have some details off a little, but the idea is the shaped charge creates an incredibly hot jet).
I don't think there's a ricochet, as (if my memory is right), bazookas use a shaped charge and that hole is caused by a jet of plasma.
Pretty high tech for the time.