I suggest an ICS MX-5 Pro MS-1.
(
http://www.nepa-airsoft.com/7/viewtopic.php?f=8&t=1526)
Worked out great for me. Split Gearbox design allows you to have several different Upper Gearboxes. Mine shot 330-335 w/.25s out of the Box. I was able to get another stock gearbox and it shoots 300 w/.25s when I need it to. I can also swap out for my ICS PCR-97 gearboxes as they are the same. Easy to work on and tweak. My one gearbox I put in it shoots 395 w/.25s for Large Field use. Decent range and rate of fire too.
This is the config I am running for Skirmish this Saturday:
ICS-MX5-Final.JPG [ 113.74 KiB | Viewed 125 times ]