SRC MP5A4 internal upgrades help

[WorcesterAirsoftRegiment1]

So I've had my SRC MP5A4 for about 4 years, and it's had some good use. It has never ever failed on me before! Therefore I would feel that I should keep it and upgrade it, rather than buy a replacement.

When I bought it, I bought the version with metal internals.

 

However, it has dropped from 330fps to 260-280fps recently.

So I figured it's time for some upgrades.

 

Could anyone suggest any upgrades for me? And the prices I'd be looking at? I've never had to upgrade the internals of a rifle before so I'm not sure what to look for.

 

The accuracy is still pretty decent despite the drop in fps.

 

Thanks

[Samurai]

A good cleaning, a new hopup rubber and a new O ring for the piston. Check the gears and the piston for obvious wear. Get new ones only if needed. Check the nozzle if it can wobble on the piston head, get new one if it does. Get SRC parts if you can.

 

If it still doesn't do the 330 fps at least, get a new spring too.