"The time interval between rounds in a cannon salute will be 3 seconds except as follows:
When honors are rendered at funerals, in which case the cannon salute will be fired at 5 second intervals. When such interval is in conflict with prescribed safety regulations for the type of cannon employed. When such interval is not feasible considering condition of ammunition and materiel, number of guns available, proficiency of gun crews, atmospheric conditions, and other local limitations." https://www.armystudyguide.com/content/army_board_study_guide_topics/customs_and_courtesies/personal-salutes-and-honors.shtml
The firing rate is a LOT slower compared to Trumps 21 gun in 2017.
"The time interval between rounds in a cannon salute will be 3 seconds except as follows:
When honors are rendered at funerals, in which case the cannon salute will be fired at 5 second intervals. When such interval is in conflict with prescribed safety regulations for the type of cannon employed. When such interval is not feasible considering condition of ammunition and materiel, number of guns available, proficiency of gun crews, atmospheric conditions, and other local limitations." https://www.armystudyguide.com/content/army_board_study_guide_topics/customs_and_courtesies/personal-salutes-and-honors.shtml