I'm not a svd expert but Slodin is right. Usually a SVD is a semiauto sniper so if you are looking for realism you should go with a semi replica (from what I've heard the best AEG SVD is by far the Real Sword).
If you're looking for a GBBR may I recommend you the We Ace VD for the realism (good recoil and the bolt lock back after the last BB fired in the mag).
In the spring world I know two companies: King arms and A&K (500 fps out of the box so a downgrade must be perform to play with it).
I hope that can be helpful!