you said your'e friends zon had 100% peirce it is capped @95% for closed realms thats why you don't always see 2-3-4 bolts/arrows peirce every time

it goes like so :

first chance: 95% (if 95%+)
second chance .95*.95: 90%
third chance .90*.90:81%
fourth chance .81*.81:66%

after that the arrow/bolt dissappears the game code disables any peirces/animations of the arrow/bolt after the random chance to peirce is incorrect value, or fourth peirce has occured