I HAVE A G&G GR16 Carbine Electric Airsoft Assault Rifle with Blowback,it started making a funny noise and wouldnt fire any ammo,i took it to bits and one of the cogs in the gearbox had 3 teeth broken from it,i got a new cog and have put the gearbox back together and connected it to the battery but it is still making a noise.does the gearbox need to be attached to the rest of the gun in order for it to work properly,i wasnt wanting to build the whole thing back up if i had to strip the gearbox back out,is there maybe something else wrong with the gun that is affecting the firing,any info would be appreciated,thanks