I was reading about the 506th FG at Iwo Jima. Eventually the historian got to the subject of gunsights and the P-51D.
I can never resolve if the K14 gyroscopic lead compensation series was very common in the late P-51D PTO or, a very, very, late introduction. It seems P-51D were more likely to have the N-9 fixed ring optical gunsight mounted in the PTO. In research of other P-51D groups in the PTO, switching from the 101Mil fixed ring N-9 to the K14 had serious ACM gunnery problems. K14 were not very reliable early on in the PTO due to humidity issues resulting in the pilots having to use the 70Mil fixed ring backup sight. The smaller ring diameter caused pilots to miss on deflections shots.
From late 1944 all K14 production went to the ETO for P-51D. P47's didn't start receiving K14 until 1945 replacing the Mk8 or British MKII fitted in staging stations in England. It was SOP for AAF fighters upon reaching England for their N-3 gunsights with 70Mil rings to be replaced with British MKII with 100Mil rings in the staging stations. You couldn't easily calculate lead against fast 109 and 190 using a 70Mil ring.
A plane 1000ft in front of you at 100mph, moving 90 degrees to your line of travel. While viewed through a 100Mil ring, travels 50Mil in 1\3 of a second. A 50cal or 20mm Hisso round travels 1000ft in 1\3 of a second. Add 50Mil for every additional 100mph in your lead or deflection allowence. Or why the Allies called 100Mil and 101Mil rings 100mph rings. The 70Mil N-3 ring was a 65mph ring.
Interesting excerpt about gunsights and a fight against Ki-84. Gunnery before the K14 was a product of the pilot's skill just like in our game today.http://506thfightergroup.org/mustangsofiwo.aspIn July, the last full month before the Japanese agreed to unconditional surrender, the Iwo Jima fighter groups received some P-51D-25s as replacement aircraft. Many of these had the lead-computing K-14 gyro gunsight in place of the old N-9 which required a good deal of skill and "Kentucky Windage" in making deflection shots. The K-14 required a smooth touch on the controls to be truly effective, but was deadly accurate in nearly any tactical situation. It could only be defeated if the target aircraft rapidly reversed its turn in a curving combat, momentarily tumbling the gyros when the P-51 attempted to follow.
One 21st group pilot familiar with the K-14 was shot down and captured by the Japanese. Under standing authority from intelligence officers, captured airmen were allowed to divulge almost any information which would ease their situation, and the 21st pilot explained about the K-14.
The Japanese took this information as a lesson learned, but the tale has an ironic and—to the Mustang pilots—a humorous end. In one of the last large dogfights the Mustangs fought over Japan, at least eight Franks were shot down because their pilots assumed all P-51s now had the K-14 when actually only a relatively few replacement aircraft had the lead-computing sight. When the Franks reversed their turns to topple the K-14 gyros they presented their pursuers with a brief no-deflection shot for which the N-9 was ideally suited! Had the Franks kept turning in their original direction they would have stood a good chance of outmaneuvering the 51s.
