Re: US Navy question
 

The ROF for the 5"/45 and 5"/62 were listed the same in the sources I found. The game standard ROF for 127mm artillery is 7, it was increased to 8 to represent the automated feed systems used by naval vessels.

5-inch-gun 54/62 Caliber Guns

Developed as a lighter weight, more easily maintained replacement for the 5in/54 caliber gun mount. It is designed to engage surface and air targets and to provide naval surface fire support for expeditionary operations. The MK 45 Mod 4 gun mount upgrade includes a longer barrel (62 caliber) that improves the guns effectiveness as a land attack/naval surface fire support weapon.

The gun mount includes a 20 round automatic loader drum. The gun's maximum firing rate is 16-20 rounds from the loader drum per minute.

Range: 13 nautical miles (14.9 statute miles) with conventional ammunition.
Type Fire: 16-20 rounds per minute automatic, conventional ammunition.

Re: US Navy question
 

P.S. (damn no edit with Firefox)

According to what I've seen the US Navy has been less then thrilled with RAP rounds and has cancelled development of naval RAP ammunition.