G1 = FN FAL, Germany’s first choice, but they wanted a licence to produce them in Germany, which FN didn‘t want to grant
G2 = SIG 510 in 7,62x51, trial gun, didn‘t make the cut
G3 = Self explanatory
G4 = AR 10 from Artillerie Inrichtingen in the Netherlands, trial gun, didn‘t make the cut
Some variants not widely adopted, like the G8.
Or other rifles tested, given a number, but not adopted (like G1 and G4).
G22 = sniper rifles AI AW I’m 300 Win Mag
G36 = HK 50