I recently bought this piece of crap...
This weekend I decided to take some advice and clean it.
I took the detachable barrel off... it was so dirty, I couldn't even see any grooves in the barrel.
Using the fishline/pullthrough method and some gunbarrel cleaner, it took me about 10 minutes to clean.
Using the same pellets as before, the grouping improved from 8cm/10m to about 2 cm/10m (sitting on chair, blasting away). this is by now means good, but WHAT A DIFFERENCE!!!
So let this be a lesson to all other noobs... CLEAN YOUR RIFLE.