Hi Renrich,
>Maybe I have missed it but what about the ballistic coeffecient of the various cannon rds.?
Here is a comparison of velocities at the muzzle and velocities at 400 m, including the arithmetic average of each pair and the flight time calculated from it (speed loss is roughly linear initially):
Code:
Weapon v0 v400 v_av T400
12.7 mm AP M2 (36" Barrel) 867 680 773,5 0,52 <- 12.7 mm Browning M2
20 mm API (from AP M75) 750 555 652,5 0,61 <- 20 mm Hispano II
20 mm mine shell 805 424 614,5 0,65 <- MG 151/20
20 mm HE 705 490 597,5 0,67 <- MG 151/20
Speeds in m/s, Time to 400 m in s
The ballistic table for the 20 mm HE shell shows a flight time of 0.69 seconds to 400 m, so the error from assuming linear speed loss is less than 3%. (I don't have full ballistical tables for the Allied weapons, so I use the same linearity assumption for all projectiles for better comparability.)
400 m were chosen because the firepower comparison I posted above shows that this was about the normal maximum engagement range expected by the USAAF, as evident in the way they harmonized their wing guns.
You might have heard of Frederick C. Blesse, WW2 and Korean War veteran and author of the first "fighter pilot's bible", titled "No Guts, No Glory". His comments confirm the short firing ranges I pointed out:
"This business of firing at greater ranges is a popular misconception in regard to Korea. Contrary to much that has been published, the Fighter Pilots who shot down more than an occasional Mig or two, got them around 400-1200 feet just like they did in Europe and the Southwest Pacific during World War II."
>I have read of, in the Korean War, Sabres making kills at high altitudes of 700 yards on Migs. A Marine exchange pilot, a WW2 veteran, witnessing this as a wingman had it explained thusly. At very high altitudes, much higher than where WW2 was fought the 50BMG had a longer effective range because of the thin air and less friction.
This applies to all projectiles, of course. With regard to the long range kills, Blesse commented in "Not Guts, No Glory":
"But, make no mistake about this -- the pilots still wanted to get exactly where they did in World War II -- six o'clock at 1200 feet or less. It was only lack of aircraft performance and poor judgment that forced him to do otherwise."
Regards,
Henning (HoHun)