Spring help!

[GhostDivisionAirsoft]

Oh font of all airsoft knowledge that is Zeroin, I have some questions.

1. What spring does a G&P M4A1 (Fixed Stock) (Marine) GP282 come with as standard (as is M100, M110, M120 etc)

2. I need to downgrade above gun, what spring would you reccommend using so that it fires at a consistent 330-340 fps ( I would guess an M100 but I'm not sure about whether that's the spring already in it, hence the first question) .

Thanks in advance guys.