I've noticed the primary ammo counter updates properly, however the secondary isn't counting things right. I filmed a sortie in a 152 where I expended every last shot, and the film starts with 350/90 (pri/sec) and I know I was out of ammo but at the end of the film as I'm landing it shows 0/5 (pri/sec). So the code that adds up or subtracts down the ammo count might need a little tweaking.
Again, minor bug, but thought I'd mention it.