Nice work, looks like a simple, non-complex H&K gun!
EDIT: Oh, duh...
EDIT2: Now to be crutial. You have forgot to put on the bolt (at least that is what I have come to understand it as). See the image for what I mean. That is there so when it is pulled back and switched into the lock position, it empties out the chamber, and when it's flipped back, it loads another bullet into the chamber. Anyway, a little H&K 101 for yah.
Keep it up,
==MeZo
"I hope all of you go straight to heaven so I don't have to deal with you again in hell!"
--MeZoFoRtE