Not bad at all. There is nothing wrong with a GPR, and everyone does have to start somewhere. Better with a production gun than not at all. You should have seen the first GPR I did. It wasn't too bad, but not as nice as yours.
The only suggestion I would make, is the inconsistency between the nicely finished stock and the aged iron.
IMHO, there should be a consistency between all parts of a gun. If the stock appears new, so should the iron work. Is just doesn't work to have part of a gun aged and part appear to be new. Otherwise, nice work.