i upgraded a friend's well l96 and had to do some filing and modding to fit parts, only clone that is worth upgrading imo is the bar10 from jg, i own one (gspec) and upgraded it with approx 500$ worth of parts and everything went fine!

which parts did you have to file? you filed the original part or the aftermarket part?

the pdi hop up... it was a bitch to align properly with the cylinder nozzle

I know there are 2 different hop ups availible; one accepts the stock barrel and one accepts a barrel that is like an AEG. the stock style is $25 and the other is like $75 , I used the cheaper option with no problem with a Modify Taper Cylinder nozzle not the stock one, and I used teflon tape on all the threads as back up to the o ring

If your just going to be plinking, go for a pellet gun, because if you are all about the accuracey then you will be somewhat disapointed with the stock airsoft guns peformance. Pellet gun is the way to go for target shooting. If your hellset on an airsoft gun just buy the L96 dont worry about upgrades and just go with it. Bolt action guns are not really entry level friendly but thats more of an opinion than anything else.