Double post (and soon to be a triple).
Testing procedure:
Simple mod of the machine pistol.
Changing Snap-shot to a range 120, damage 150, high accuracy shot, 5TU.
3-shot remains normal.
Changing Full-Auto to a range 120, damage 2, 120 shot burst, 5TU.
Magazine upped to 240 shots.
Two soldiers(1+2) in squad will use Full-Auto for kills. The rest will use Snap-shot. One soldier(
will also try and kill-scum on Full-Auto (the percentage to-hit still comes up).
I'll report how they do on "Close" skill gain compared to missions/kills.
Initial thoughts (4 missions in) is that hits count for exp. At least, they seem to. Soldier 2 has more kills on full auto, but also has far higher skill gain. I'll report testing after I've got about 20 kills on each type of soldier, with soldier 8 only kill scumming. I might also just Full-Auto at walls with Soldier 7 to see if there's skill gain without hitting anything.