The one test I did was using the single Hispano on the P-38 from a range of about 100 yards hitting the tail cones of the Bf110G-2, Mosquito Mk VI, Lancaster Mk III and B-17G. It consistently took 2 shots to removed the 110's tail, 3 shots to remove the Mossie's tail, 14 shots to remove the Lanc's and 17 shots to remove the Fort's.
This was in AH1 though.