Good place to start

[RhoXi]

Another vote for the Classic. I finally got out to the field this past weekend and only brought guns I haven't used in a game. I had like 5 guns with me but ended up only shooting my classic power feed automag. It was just too good and I had no problem hanging with the electros. The only mod I have is a RT on/off but now I think I want a lvl10 too.

I'd hunt for a bit and score a plain jane classic or minimag then throw a rebuild kit at it for good measure. Then after a while decide if it needs any changes.

[MrBarraclough]

Get a classic Automag or Minimag with a Level 7 long-nosed foamieless bolt. Put a Doc's Machine barrel adapter in it so you can run Autococker barrels and (more importantly) rubber finger detents. Swap in an R/T on/off (but not a ULT). Use a stock frame and rail. Do not monkey with the trigger rod adjustment on the stock sear.

This will be the least finicky, most robust and reliable configuration that will still rip without you having to "tune" a damned thing.

Edit: And feed it with a constant pressure force fed loader such as a Halo or Rotor.