The following tables adapted from information given in "Naval Weapons of World War Two" by John Campbell show the USN's anti-aircraft successes between October 1944 and January 1945:
[SIZE=+1]Kamikaze Actions[/SIZE]
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Weapon Planes Shot Down Number of rounds per plane
5"/38 using AA Common 19 1,162
5"/38 using VT 24.5 310
3"/50 using AA Common 6.5 710
40 mm Bofors 114 2,272
1.1" MG 1 2,231
20 mm Oerlikon 62.5 8,972
0.5" MG 2.5 28,069
Generally speaking, Kamikaze actions were at very close range with the aircraft closing fast upon their intended target. These sort of engagements were very difficult for weapons firing time-fuzed ammunition, as the rate of change in the ballistic range to the aircraft also meant that the fuze settings needed to have large changes from one round to the next. Any lag or delay in getting a particular round into the air after its fuze had been set meant that its detonation would be too far away to reach the target aircraft. The VT fuze eliminated that problem, as noted by its far smaller rounds per aircraft rate.
[SIZE=+1]Non-Kamikaze Actions[/SIZE]
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Weapon Planes Shot Down Number of rounds per plane
5"/38 using AA Common 33.5 960
5"/38 using VT 20 624
3"/50 using AA Common 4 752
40 mm Bofors 46 3,361
1.1" MG 0 (4,764 total)
20 mm Oerlikon 50.5 7,152
0.5" MG 3 15,139
In this table the advantage of the VT fuze, while still significant, is not nearly so pronounced as in the previous table. This may be due to the fact that the rate of change of the attacking aircraft's ballistic range did not change as rapidly as did a Kamikaze aircraft, thus allowing the fire control computers more time to process the incoming data and produce better time fuze settings. It is interesting to study the success rate of the 3"/50 gun, as this weapon was adapted post-war with automatic loading and VT fuzes to replace the 40 mm Bofors on most US warships. Even without VT fuzes, the shoot-down rate of the smaller weapon compares favorably to that of the 5"/38 firing VT-fuzed ordnance. Although, the high numbers for the 5"/38 may be a result of the fast firing rates of these weapons and the fact that nearly every warship destroyer-size and larger carried several of these weapons. So, even a pair of destroyers could fire over 200 rounds per minute.
For more information on the VT fuze, see the Ralph Baldwin book, "The Deadly Fuze - Secret Weapon of World War II." An analysis in this book of the 278 aircraft shot down by VT fuzed projectiles between October 1944 and August 1945 indicates that only 46 of these would have been destroyed if time fuzed projectiles had been employed. However, Will Jurens, noted ordnance authority, estimates that Baldwin's 6:1 ratio apparently assumes that 70% of the VT fuzes worked. A 50% failure rate - the Navy's lower limit of acceptability - meant the effectiveness ratio was closer to 4:1. In comparison, mechanical time fuzes such as the Mk 18 typically worked about 90%-95% of the time.
There are a lot of pitfalls in this sort of analysis, and it is extremely difficult to arrive at meaningful numbers. With this caveat firmly in mind, I will quote some of the better figures for World War II:
Type of Attack Planes Shot Down Rounds per Plane 20 mm 40 mm 5"/38 MT* 5"/38 VT
Kamikaze 24 27,200 6,000 1,000 200
Non-Kamikaze 41 30,100 4,500 1,000 550
* MT = Mechanical Timer (i.e., Time Fuzed AA Common)
These figures are from the Special Defense Operations Research Group (SpecORG) study, "AA Defense of the Fast Carrier Task Force - 24 October 1944 To 21 March 1945", Anti-Aircraft Study No. 8, revised 11 September 1945. They address only carrier task groups, for which the best data were available.