What's the point of heavy flak?

Originally Posted by Threadfin

I don't think flak shells in WW2 had proximity fuses. They are fused to explode at a certain height, they are timed fused.

After a bit of research I have to admit that they weren't proximity fuzed. The characteristics of the 3.7cm are as follows:

Muzzle velocity _ _ _ _ _ 2,690 f/sMaximum horizontal range _ _ _ _ _ 8,744 ydsMaximum vertical range _ _ _ _ _ 15,600 ftTheoretical rate of fire _ _ _ _ _ 150 rpmPractical rate of fire _ _ _ _ _ 60 rpmMaximum effective ceiling with self-destroying tracer ammuniion. (A new shell has been introduced, which is self-destroying at 9,185-11,480 ft. after 7-10 secs.) _ _ _ _ _ 13,775 ft with 14 secs time of flightAutomatic, recoil-operated; the firing mechanism can be set for single-shot or continuous fire as required. The ammunition is loaded in clips holding 6 rounds.Weight in action _ _ _ _ _ 3,100 lbs (approx.)Elevation _ _ _ _ _ -10° to +85°Traverse _ _ _ _ _ 360°Length of barrel _ _ _ _ _ 50 cals (6 ft)Ammunition—two classes, as follows: (i) Self-destroying HE tracer vvith percussion fuze (weight of projectile, 1 lb. 6 oz) (ii) AP tracer (weight of projectile, 1 lb 8 1/2 oz)

So it appears as if they need a direct hit to damage an aircraft, and self-destruct (explode) at the end of their range.

credit: http://www.lonesentry.com/manuals/ge...t_aa_guns.html