The ARES/STAR guns will have quickchange springs. My beef with them though is the microswitch that tends to fail pretty quickly. You can get a replacement off Digikey or Mouser and I used to have the model number of a similar switch with similar specs but I lost the piece of paper I wrote it on (Kailh should make a similar microswitch though they're quite a big company).
King Arms are pretty solid and cheaper as well, needs 1 part replaced eventually due to wear and tear (it's the cutoff lever, which prevents you from firing in semi once it gets worn down enough).
BTW have you not met with an AV rep yet? I would have suspected that you'd have your tag by now.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE