Our own DonP wrote a great article here:
http://www.unconventional-airsoft.co...mation/svd.php
The G&P gas-powered version needs a LOT of work to even be used at a game.
The Guarder "dragunov" kit slapped on a TM AK47S is not really a Dragunov - the reciever is the wrong length - it's more like a Romanian PSL. But it is electric (and thus can fire semi-auto, even full auto), parts are easy to come by, and it's easy to fix.
The Jin Gong dragunov is the same as above, but not as nice looking.
The King Arms/AtoZ version is highly regarded as accurate + powerful, but is manual cocking, so no semi-auto sniping for you.
The PDI Dragunov is gas powered, semi auto, out of production for many years, impossible to find parts for, and insanely expensive.
This are your chioces, unless you want to attempt a scratch-build.