There's "actual physical range" where the bullet still travels, then there's "effective range where you can realistically expect to hit anything."
While the 50cal round can physically penetrate 2x 1/2 inch steel plates 3 feet apart from each other at a mile out, there's no way this can be done other than with a sniper rifle, a steady prone firing position, a well marked target, a non-moving target, and a highly advanced optical scope. Oh, and only with 1 round, not a machine gun firing 600 rounds a minute.
The realistic effective range of 50cals on armed WW2 aircraft was 300 yards (most "killing" combats being far closer than that). Many things including dispersion of the rounds, vibrations of the gun, the wings of the plane, turbulence of the air, the shaking of the gunsight, human error, imaccuracies in the gun mount or optics, means that the way AH bombers are modeled is way way above and beyond their historical capabilities. A good portion of this is the fact that bombers in AH fly with 1/4 fuel, meaning they fly faster and climb faster than historically, and that they run at full throttle, reducing closing speeds of most attackers to less than 50mph, where historically attacking fighters had several hundred MPH with which to make slashing attacks.
So, even though it's not a total fix, if there was some way of slowing bombers down in this game to historic levels, that would go a long way to reducing the 1.7k hits they seem to get so frequently. The guns themselves could use some tweaks too, but this would solve a lot of problems.