interesting citation on the effectiveness of "keel" shots

[Platapus]

I will be posting this in the SH4 forum as I would be very interested in reading other people's thoughts on this topic.

on 26 March 1943, the Bureau of Ships (BuShips) drove another nail into the Mk. 6's coffin. In a letter from BuShips chief, Vice Admiral E.L. Cochrane to Blandy [BurOrd chief] regarding the most effective depth at which to achieve torpedo hits, Cochrane took the opportunity to comment on the supposed advantage magnetic influence explosions beneath a ship's keel:

"Except for ships fitted with torpedo protections systems, the Bureau [BuShips] is unable to see any great advantage in obtaining non-contact hits under the bottom" *

The Bureau of Ships housed the Navy's foremost ship designers and naval architects. The BuShips' engineers studied torpedo damage on scores of ships, including those of foreign navies. For them to conclude that the mK. 6 magnetic feature offered no advantage over contact exploders (except on large capital ships) was a devastating revelation to BuOrd, who cited the effect of magnetic influence explosions in defense of charges levied against the MK 6 by the operational submariners.

Newpower, A (2006) Iron Men and Tin Fish London: Praeger Security International p. 147

* Citation for Cochrane quote:

Letter from Vice Admiral E. L. Cochrane to Blandy, 26 March 1943, RG 38, Correspondence of the Office of the Chief of Naval Operations, National Archives

This is an interesting piece of information. I have always read that under keel shots are the preferred way to destroy a ship. But in my more cynical moments, I wonder if this is not one of those issues where because it is repeated so many time over so many years that it becomes accepted as fact.

In reading this type of information, one must always keep in mind the intra-service rivalry between BuOrd and BuShips. But I find it hard to believe that Vice Admiral Cochrane would deliberately lie.

And as always, when interpreting and analyzing history, it is most important to only consider the information the participants had at that time.

So my question is: Only considering the data available in or before 1943, Do you think that Admiral Cochrane's comments were valid?