I wonder how much live main battery ammunition is still onboard the Arizona

For what it's worth, I posted some new Arizona documents I found on a trip to the National Archives a year or two ago. One of them is a post-war analysis of the magazine explosion, and based on paragraph 16 of that document I highlighted the space that started the conflagration. Main battery shell storage was close enough to the powder that there was likely nothing left to salvage, even had it been feasible. Exploded 5" powder cans were found on the beach on Ford Island, roughly 350-400 feet away (paragraph 12) and the magazine for those were just aft of the 14" smokeless powder magazines.

If you watch her explosion, there are a lot of secondary explosions to the right of Arizona shortly after she explodes (4-5 seconds into that clip) - I believe this to be powder and shells that were blown out of the ship by the explosion. The explosion was forceful and violent enough that unless a shell was driven down to a deck that flooded nearly instantaneously, I doubt it survived.

 

As noted previously, the shells were stored in the barbette, in both rotating and non-rotating areas. The external aerial detonations were indeed 5" powder cans and illumination rounds. The barbette most probably protected most of the 14" shells forward, despite the intensity of the magazine explosion. I invite you all to research "shock cocoons". The theory is fascinating and explain why the forward part of a heavily armored hull was ripped apart, but simple 1/2" steel pins held the hatch and awning assemblies on the hatches just outboard of barbette 2. Tracy, this was in one of the chapters that I did not put in the book (IN REPOSE) as I did not have it finished at the time we went to press.

 

For a bit more info on this, pick up the book "IN REPOSE" - Diving on the USS Arizona with the National Park Service. Great read, lots of information, all true, from a guy who has been there, done that!