I can see there's a lot of guys here that never spent (wasted?) many of their youthful afternoons shooting .30-06 caliber rifles loaded with surplus military ball ammo at old abandoned cars at ranges up to 300-500 yards.
I assure you, an old 50's Chevy has MUCH thicker steel than the thin aluminum on a WW2 aircraft. .30 Military ball would whistle right through car doors, in one side and out the other. Hydraulic lines, control cables, fuel lines, fuel tanks.. like wet tissue paper.
... and this is rilfe caliber ammo.
A .50 BMG is like superman on steroids in a 'roid rage compared to a rifle caliber round.
Basically, some folks think it's too easy to shoot things down in AH. They want the fight to "last longer" and are apparently willing to pork any data necessary to achieve this end.
Stick to what the rounds actually did in trajectory, energy, velocity and all the related "known" factors.
Then, as Modas said, you do the best you can with the damage model.. and as I just said, I personally believe there's a lot of you folks that don't know what military ball ammo will do to a lightly built WW2 fighter that's primarily aluminum and lighter metals.
My brother-in-law just shot a bolt action .50 loaded with old military AP ammo at a 1" steel plate hanging from chains at 100 yards. One inch steel plate. He aimed fired and the plate did not move at all.. nothing.. thought he missed. He shot again.. same thing. He's a proficient rifle shot, so he walked out to the plate. Two .50 holes clean through it. Went through so easily, they didn't even make the plate move (bout 100lbs of steel in the plate). He said the holes were "clean".. no slag, no rips, tears, edges.
Will heavy MG crack any engine block in any WW2 fighter? Yep. Will it go through hardened armor plate at close ranges? Yep. Will it go through plexiglass? Yep, form a long, long, long range.
Don't underestimate the pentration of even rifle rounds on thin aluminum.. even at long ranges.
