For a real gun, Beretta M92F is different from Mod.92FS. For the airsoft, their outlook are close to each other.
When the mag. is full of gas, you can't insert more gas.
In Hong Kong, You can buy the SVD from different brands. A long time ago, a china
factory called A&K had produced a powerful SVD, but it had sold out for a long time.
Now, you may have a look on the SVD in a shop called `CA', which is a HK factory.