Yes, the sight is a bit off. I don't really care. At all. It's a conversation/display piece first, a plinker second as far as I'm concerned. I bought the gun because I will never be able to afford a real STG and likely never a PTR-44. BD-44s cannot be imported..
so this .22 is better than an airsoft replica and I'm fairly happy with it. If I want to do some serious shooting, I'm getting my Savage bolt gun.
The action is actually a Ciener .22 copy. I haven't had a single issue with it, and it's a MUCH better system than that in the GSG-5.
Fun gun, reliable. Just for the record, it's an MP-43/1 "clone". The muzzle nut....
I wouldn't use lube.. just attracts more dust. Just put some LIGHT grease on the rails the bolts slides on. Nothing else.