Hi,
Regarding saluting guns and gun salutes. here in the definative answer from an Ex W.O. gunner who is now part of HMS Belfast's management team.
I have attached Chapter 11 (Procedures onboard ship) of BR 1834 (Bit old now) Ceremonial Drill Hand Book, which you may find helpful.
As to guns, we only ever rigged 3, 2 on the side of the salute and the third on the opposite side. Dependant of how many guns to be fire, the cartridges were divided between the 2 guns with the odd round going to Gun number 1.
The third Gun on the opposite side was the misfire gun, it would have the same amount of rounds as Gun 1, just in case it misfired on the first round.
The Salute was fired alternately between the 2 guns on the engaged side, with 5 second intervals. Misfire wait time is / was 30 minutes. Once a gun misfired it took no further part in the salute.
I hope this helps all those interested in rigging a gun salute for a ship entering harbour etc.