I made the virtual 30-round mag mod I mused about!
Couple things though:
1. The gun will always fire a burst (if you're at 2 rounds left, and you shoot a burst, you'll still shoot a 3 round burst even though you technically only have 2 "rounds" left in the mag.)
2. Why? Cutting off a burst in mid-burst was just too much work to bother programming for this quick mod.
3. Rounds fired in fullauto is estimated. It's pretty accurate, but not perfect. It's "good enough" (see #2 above

)
4. The switch is one that just happens to be big enough to trigger when a mag is inserted. I was really lucky I had one in my junk box. I don't have a specific part number or anything, sorry.
5. Tactical reloads work! (Mag change "resets" to 30 rounds)
6. Gun will not fire without a mag inserted.
Video Download
Splashx: Regarding the programming, see your PM about the same question.