Thanks for the comments guys
I have no idea of the fps at the moment as it wasn't cronoed at the weekend :/ I can estimate it at around 300fps as I am using an M90 spring because the local shop I go to didn't have M100s in stock and the M110 I have would put me over the 374fps limit for AEGs.
It did receive a fair few compliments from the guys I regularly play with and was asked if it was a dragunov so many times by the newer players :

, including the one who pooed his pants when he ran into a doorway and straight into the G3's business end lol.
It sounds fantastic and shoots quite well except only on full auto so I need to sort out that problem. but I had major feeding issues with my mags and ended up using my vsr for most of the day (which is another story

) the mags would, when they felt like it, feed about 20-30 bbs then stop feeding, I am using 130rnd mid caps.
as far as the gearbox is concerned I put a bearing spring-guide in (modified v3) and bearing piston head and a modifyed v3 silent cylinder head with mouse mat padding on it. the gear set was swapped out for a modify set :
http://www.airsoftworld.net/modify-upgrade-parts/modify-smooth-gear-set.html
the cylinder is a teflon one I bought for my g36 and the nozzle is a modified G36 airseal one.
the reason there are so many v3 parts is that I was trying to spend as little money on parts and I had them lying around.
the motor is the standard JG one as is the barrel and hop rubber.
the barrel was taped, hop was ptfe taped and the nub replaced with a H type one.