Over on warships1 that comment about HACS would generate another 20-page thread comprising mostly of someone raging at USN overclaiming! He'd have something to say about the 5.25"'s rate of fire too...
oh yes educational reading.. and for some reason the HACS seems to have generated a lot of heat.
As I see it any ship borne HAA system was not sufficiently effective to prevent air attacks even during the later stages of WW2 in the pacific.
Late war German experience with land based flack suggested that variations in the timing of mechanically timed fuses rendered predicted fire mostly irrelevant thus several thousand shots per one hit. They improved matters by removing the timing and firing sabots s at higher velocity designed to explode on impact.
I suspect the techniques used by the RN tended to minimise the Bad points of mechanically timed predictive fire
1) quickly calculated firing solutions using estimated predictions rather than mechanically calculated Tachometric solutions
2) firing salvos so that all the shells exploded in a similar time and space making a larger area lethal to enemy aircraft.
The best solution was of course proximity fuses but they were not available until 1942
in the meantime a look at the AA casualties inflicted on the LW by convoy PQ18 and the AA casualties caused by the USN at midway one to suggest that If HAC's was a piece of Shit system then the Ml 33 & Mk 37 systems were indescribable.
Just of course an opinion and many will disagree.