The salute originated with cannons. Firing a cannon unloads it and makes it unusable until reloaded, so the custom of firing in greeting came into use. This is sort of like a handshake proving you have no weapon.
Ships would fire seven cannon. Land batteries had more powder on hand than ships and so they fired three shots to every one fired from the ship. The reason for choosing seven and three is probably a naval superstition, since they have been considered mystically significant numbers for centuries. Eventually when powder improved and more could be stored and carried the ships also adopted the 21 gun salute.
seven guns fired three times each, for a total of 21 shots
The 3 volley salute is an adaptation of the 21 gun salute. 7 guns are fired 3 times. This is a common mistake. The 3 volley salute just happens to be preformed with 7 guns (but may be performed with a few as 3 guns), but it does not constitute a 21 gun salute. A 21 gun salute is preformed by a battery. The 3 volley salute originates from an old custom of removing the dead from the battle field to allow the fighting to continue. The armies would then fire 3 volleys to indicate the dead were cleared and they were ready to go back to fighting.
3 volley is not 21 gunsyou appear to be confusing the 3 volley salute, executed at the grave of a veteran, with a 21 gun salute. 3 volley salute, even if accomplished with 7 rifles, is not a 21 gun salute. It is simply called a 3 volley salute using 2 to 7 rifles. Execute the 3 volley salute facing north, if possible, over the casket. Keep your distance from the mourners. keep the volleys clean - no popcorn.21 gun salute is done with cannon. one shot at a time, in 5 second intervals unless it is a 21 minute gun salute. 21 guns only for POTUS funerals, otherwise, the number of guns fired, 13 to 21, according to status of high officials and ranking officers.21 guns (cannon) also fired at noon for Washington's birthday, Memorial Day, Independence day.
A soldier gets a 21 gun salute.
The gun salute was standardized in 1841 to include 21 guns, 3 shots per gun.
The 21 gun salute is fired and then the playing of taps. On the first note of taps servicemen in uniform and retired servicemen come to Present Arms. (hand salute)
Tradition. 21 shots is the highest salute rendered.
The gun salute (which usually isn't a 21 gun salute). Three volleys will be fired, the firing line will be brought to the position of present arms, then Taps will be played.
To represent the 3-gun salute. Each firer shoots 3 rounds in volley. If there are 5 honor guards, then it appears that there is a 15-gun salute, but each fired weapon doesn't count as 1. Many confuse a 21-gun salute with having 7 or even 21 guns, but in reality there is a battery of field artillery pieces.
A Royal Salute that is performed at military functions and funerals has 21 guns that fire. If cannons are used it is usually a series of seven cannons that are fired three times each. The common method is to have seven soldiers fire a rifle three times each.
Salutes performed by firing guns ranks from a low of 5 guns, to the highest possible salute- 21 guns. A "21 gun salute" is paying the greatest tribute possible to the person or persons being saluted. Some additional information on this subject for you: http://www1.va.gov/opa/feature/celebrate/gunsalut.asp
21 Perfect in a Game (of Blackjack)