Urchin;
From a previous post:
In a parked M-16:
How easily could you kill a parked P-51 at 760 yards?
How easily could you kill a parked B-17 at 1320 yards?
What does this have to do with buff gun performance?
The 2 examples above illustrate the real-world energy difference between a B-17 exchanging fire with a P-51 at 1000 yards (6:00 chasing at 250 mph).
Why the difference? Get a A6M up to 300 mph, auto-pilot on and kill the engine. Watch the airspeed indicator needle drop like mad the instant you kill the engine. Now do the same thing at 200 mph. The needle still drops sharply, but not as fast (300 - 250 = 5 sec., 200 - 150 - 7 sec.). Faster moving objects have more air drag than slower moving ones, a lot more (drag is a function of the square of the speed, if I recall).
Imagine: A P-51 chasing a B-17 at 1000 yards, both planes are exchanging fire and are traveling at 250 mph.
The B-17 tail gun round:
When a 50 cal. bullet leaves the muzzle of the tail gun in a B-17, it actually has a slower airspeed than a 50 cal. bullet fired from a fixed ground fired gun (about 367 fps slower if the buff is flying at 250 mph). This means that it will lose speed and energy at a slower rate than the ground fired gun (even though it has less speed and energy as soon as it leaves the muzzle). It's target (the P-51), is actually moving toward the point in space from which the 50 cal. bullet was fired, so this round has less than 1000 yards to travel before colliding with the P-51. When it collides with the P-51, it instantly gains 367 fps to its speed and energy state (the speed of the P-51).
The Mustang round:
When a 50 cal. bullet leaves the muzzle of one of the P-51's guns, it is actually going faster than a 50 cal. bullet fired from a fixed ground fired gun (about 367 fps faster when the stang is flying at 250 mph). This means that it will lose speed and energy at a faster rate than the ground fired gun (because is has more speed and energy as soon as it leaves the muzzle). It's target (the B-17), is actually moving away from the point in space from which the 50 cal. bullet was fired, so this round has more than 1000 yards to travel before colliding with the B-17. When it collides with the B-17, it instantly loses 367 fps from its speed and energy state (the speed of the B-17).
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The actual math:
250 mph is equal to 367 fps (the speed of the planes).
A 50 cal. round weighs 708 gr. and is moving 2845 fps, right out of the muzzle.
Ballistic Coefficient: 0.700
Drag Function: G1
I used the following link to crunch the numbers:
http://internet.cybermesa.com/~jbm/ballistics/traj/traj.html The B-17 tail gun round:
Leaves the tail gun at 2478 fps (airspeed). 2845 fps (50 cal. muzzle velocity) - 367 fps (aircraft speed) = 2478 fps (true airspeed of the 50 cal. round)
The round travels 840 yards (before colliding with the P-51) in 1.284 sec and has a final velocity of 1558 fps.
1558 fps (the speed of the round just before impact) + 367 fps (the speed of the P-51) = 1925 fps (the true impact speed of the round). A 708 gr. round traveling at 1925 fps has 5800 foot pounds of energy.
The Mustang round:
Leaves the Mustang's gun at 3112 fps (airspeed). 2845 fps (50 cal. muzzle velocity) + 367 fps (aircraft speed) = 3212 fps (true airspeed of the 50 cal. round)
The round travels 1180 yards (before colliding with the B-17) in 1.497 sec and has a final velocity of 1750 fps.
1750 fps (the speed of the round just before impact) - 367 fps (the speed of the B-17) = 1383 fps (the true impact speed of the round). A 708 gr. round traveling at 1383 fps has 3010 foot pounds of energy.
So there you have it.
In the B-17 / P-51 chase example, the rounds hitting the B-17 have 3010 ft.# of E. and the rounds hitting the P-51 have 5800 ft.# of E.
By the way, a 50 cal. round fired from a fixed point (like a parked M-16) has 5800 ft# of E. at 760 yards. It drops down to 3010 ft.# of E. at 1320 yards.
That's why bombers' guns seem so powerful at longer ranges.
Back to my original statement:
In a parked M-16:
How easily could you kill a parked P-51 at 760 yards?
How easily could you kill a parked B-17 at 1320 yards?
The greater the distance between the buff and the fighter, the more exaggerated this effect becomes. At close ranges, however, the difference between the two practically go away.
To kill buffs with a fighter, you must get in close, WITHOUT GIVING THE BUFF GUNNER A GOOD SHOT AT YOU, before you have the firepower advantage.
There are many effective ways of doing this, but that is a whole new topic.
eskimo
