The snowguns are using Q magic and only work inside the Winterwonderland. once it's over you can say goodbyy to it for the rest of the year.
You can't shoot other players, at least of the same faction.
What you get hit with is probably just regular snowballs, an "enemy" faction snowball has a chance to knock you over, which I painfully had to endure while doing my daily race.
A couple KDF players found it funny to grief me the whole distance.
I won the race, but just barely.