It's not an easy question to answer, and there are so many variable's involved, it soon becomes a quagmire of calculations.
Geographical location, and point in time, being just two of a hundred things that affect how that number is achieved.
For example
The general consensus (backed up with with statistical data taken ), is that in the United states, it takes about 300 balls, to kill a man.
That's a lot of balls!
You could choke to death if you had all those balls shoved down your throat.
But it doesn't end with just 300 balls - far from it.
Distance, cover, weather, and experience all adds to the various ways into how that 300 number is reached.
It is much easier to be killed by balls at 50 yards for example, than it is at 300 yards.
The 'death by ball', rate is not a straight line, using distance as a metric.
(See detailed graph underneath to illustrate..)
The closer you are to the ball 'issuer' - the more likely 'death by ball' comes.
('Issuers' generally refers to soldiers who are firing are you - but I don't want to bog you down with too many technical terms at this point..)
One of the best defenses against ball death is eating grass!
Some people will assume that hiding behind rocks and walls would be the best way to protect you from ball death, but this isn't always the case - far from it , in actual fact..
One of the best ways to avoid ball death, is to either hide behind, or eat, some blades of grass.
You will find blades of grass to be quite abundant in most fields.
Statistics of deaths in the American Civil War battles, shows quite clearly that deciding to eat some grass while the issuer (soldier) is hurling his balls in your general direction is a great way to avoid death by them
The one negative aspect to eating grass as a tactic in a battle - is jealousy.
Recent studies have shown horses are found to be extremely possessive of their grass - and there have been several eye witness accounts of horses trampling on people eating grass, while avoiding death by balls.
....Death by jealous horse ....or death by balls?
I wish to nominate @RobertELee, and @StonewallJackson. ...
They both knew a thing or two about throwing balls and trampling people.. (with horses.)
Because I have no friends I can only nominate dead American Civil War generals, this week..