My "theroy" on the turret explosion on the Iowa is that it was caused by updated systems attempting to fire the guns too rapidly.
Newer powder bags are much thinner than those designed in the 30's for use in those guns. They looked into "over ram" which causes a particularly unstable condition due to settling in the suspension material.
And were based mostly on the condition of the breach control during investigation which indicated it "should" have been open. The gunner's chair was so deformed by the blast I doubt the position of the breach control could be confirmed prior to the explosion.
All tests where inconclusive and so far the Navy has not determined a cause. There are other investigations still going on but, there will more than likely never be an official determination.
All I can tell you is when I saw the video of the guns firing and the subseqent explosion I knew in my mind the cause.
Hot breach, AFTER the ramming process with a partually open breach. Those guns where simply not being purged correctly.
If you watch the video the timing was almost perfect for that batteries next salvo, and where firing much too fast.
Obviously since without official determination of cause the public will never know for sure, run a stop watch when watching the video and you'll make up your own mind.
The powder bags, ripped or otherwise along with settling, touched off by over-ram by themselves unless, something comes up in current independent tests (I believe someone is still running them) have been eliminated as cause.
I do however agree with Jason, ammo use per month is way to high and always has been.