If it's the newer JG enhanced version, I garauntee that it does have metal bushings. May not be the best metal bushings, but they're better than plastic.
First off, you'll probably want to put a new spring in the gun anyway. The new JG's all come with M130's and they seem to always shoot over the 400fps mark which is too hot for pretty much all field limits. The upside is that if you do as Dragon mentioned, make your airseal the best it can be, you can get good velocity from weaker springs which in turn will make your trigger response higher, and your ROF higher while also helping yout gun last longer due to less stress be put on your other parts. There are 4 key areas to adress with your airseal. If all the areas are adressed properly you should have absolutely have no problem getting ~365fps off of only an M100 spring.
First off, polish your cylinder with some Brasso (you can get it at Walmart). Next you'll want to seal your cylinder head with silicone sealant. It works wonders, trust me. To do this, make sure the inside of your cylinder has already been polished and has been cleaned of all polish residue and is dry. Next, add a small beed of slicone sealant around the O-ring of your cylinder head and put the cylinder head into the cylinder. Quickly place the cylinder and cylinder head set back into your GB and put both halves together to allow it to set up with everything in proper alignment. Note that nothing else has to be in the GB for this step. While you're doing that, remove the factory O-ring from your piston head and replace it with a standard #14 o-ring. You can get these o-rings at Home Depot, True Value, Lowes, or where ever. Lastly, your air nozzle. Really the only way to remedy this area is to replace the factory one. I find that a good majority of air is lost here due to poor seal. My personal recomendation is the AIM brand o-ring air seal air nozzles. They're tough and seal better than any other nozzle I've used. Jon can more than likely get you one or he may have other brands that will suffice. This part is usually quite cheap and for the performance it adds, it's totally worth every penny in my opinion. Some guys go further by sealing the bucking to the barrel. It can work, but I've gotten minimal returns from a job that is a total PITA.
Allot of the newer JG's are also coming out with one piece hopup units. This a good thing. They may not be as good as an aftermarket one, but still better than the old two piece. A G&G hopup bucking is my #1 recomendation. They're simply amazing. They work well on guns shooting ~280fps to guns shooting over 500fps. The also don't harden in cold temps like almost all other buckings do. I always flip mine inside out and rough up the little 'nub' part with some 1000+ grit sand paper. It's like an instant 'break in' and will also make the hopup more reactive and more consistant.
Those JG tightbores actually aren't too bad. Don't let anyone tell you for one second that you need a 6.03 or 6.01. I'm starting agree with allot of the older more experienced airsmiths that the term 'tightbore' is just a BS name to help sell stuff. I'll tell you a little home remedy to make you're barrel REALLY perform. Remember that Brasson stuff I mentioned above? Yeah, break that stuff out again. Get a (prefferably one piece) cleaning rod and put the Brasson on the patches and polish the inside of that barrel. Some barrels only need a couple passes, some need 4-5. Jus keep going until after you run a dry patch through it that it looks like a mirror in there. Next, and here the real secret, Rain-X. Yeah, get some of that and be sure that it's the old pure rain-x and not the rain-x with glass cleaner and junk in it too. Run a couple of passes of that through there just like the directions on the bottle say to do with glass. Once you've done all that, you have a polished and sealed barrel. Now the brass won't tarnish over time and the rain-x helps keep dust from accumulating in the barrel along with resisting adverse spin if the BB should hit the inside of the barrel durring it's travel.
Your motor is more than likey one fo the JG Super High Torque motors. Let me tell you, I've used allot of different motors, and those are supringly one of the better motors I've used. I don't suggest changing it unless you absolutely have to. Those motors are REALLY torquey and provide good trigger response and ROF.
Next, fixing your angle of engagement is a vital modification to help the longevity of your piston and your gun. It's pretty simple to do. Actually it's one of the easiest and valuable things you can do to prolong the life your gun.
Dragon brought up a good point with the batteries. I recently bought my first 7.4v lipo. I love it. It give a little better trigger response and ROF than a small 9.6v without wearing out your motor fast like some 11.1v lipo's can. Problem is that if you really want you lipo to last you, you'll want a balance charger to go along with the battery. Jon can more than likely hook you up in that department as well.
I try to do all those basic upgrades and mods to ALL my guns now. I've been getting better accuracy, range, overall performance, and longevity out of all my guns after doing this.
Hope this helped! Good luck!
