i have an nr90 (a green one) , may be previous to the gr2 and it works a treat. just got it out of the shed this week after a year or two, charged the battery, give the gas can a few taps and shakes and away we went.
IIRC the battery goes flat if you leave it in the gun (i think the flashing green light does not stop so eventually drains the battery) apart from that, no problems.