I have tried this two different times (as in two different 'lives') and I wasn't able to fire my gun either time.
First time was Yesterday 07-01-2014
Second time was today 08-01-2014

Thing is, the gun works for others playing on the same server, both my friend I was playing with, and random douche that shot me.

What happens is, I pick up the gun, and later I get a magazine (with 15 bullets in) so I load the magazine in, and I wasn't able to shoot. I've tried emptying the magazine as well, but to no use.

I read around and wasn't able to find a bug report on this, however I found some threads describing a similar problem:
http://forums.dayzgame.com/index.php?/topic/53622-my-pistol-wont-fire/
http://steamcommunity.com/app/221100/discussions/0/648814844022410843/
http://r2.reddit.com/r/dayz/comments/1tsr6k/pistol_wont_fire/