Can anyone explain to me the art of chainfiring? I don't think I've ever experimented with that, and I'm currently trying UV AoMC, on which I suspect it may come in handy...
Here's how it works:
On the first (initial) turn the weapon fires 2/3 of its standard shots, rounded up.
On the second (warming) turn the weapon fires a standard amount of shots.
On the third (full) turn and all subsequent turns the weapon fires 3/2 of its standard shots, rounded down, until you stop chainfiring or your weapon runs out of ammo (in this case, of course, you will only fire whatever number of shots you have remaining).
So for example a normal chaingun would fire 3, 4 and 6 bullets respectively, while a F-modded minigun would fire 7, 10 and 15 bullets.
Now, you can switch targets between turns. If you do, however, the weapon will pan from the previous target to the new one, and will fire shots in an arc between these targets - one shot per ~30° of arc. So if you first aimed directly north and then switched to directly east, two shots would be "lost" (fired at 30° and 60° angle respectively, and these can hit targets standing in their path), and only the rest of the volley would hit the new intended target.
Good luck with that UV AoMC.
EDIT: If I read the code correctly, then extra shots granted by Triggerhappy are counted towards the _base_ number of shots (i.e. before multiplications for the initial and full turns of chainfiring).
