It should be but it's probably a good idea to get another battery with more amperage so the battery will last longer (generally you can approximate that 1 mAh = 1 shot, 600 mAh = 600 shots more or less which might be OK for an indoor/short game but doesn't cut it for a day long game unless you're easy on the trigger and definitely won't cut it for a milsim).
I would suggest putting a PEQ box up front with a brick battery inside even if you're easy on the trigger. I have a 2800 mAh 9.6V myself and I definitely pick my shots but the extra insurance of the extra amperage is always comforting.
NB: 8.4V (7 Cells at 1.2V) is a pretty standard voltage especially for TM's.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE