Ian from Forgotten Weapons goes through how DMR's changed over years starting iwth WW2.
http://www.forgottenweapons.com/history-of-the-designated-marksmans-rifle-video/
Also, he blogged about a nice video from capandball discussing SVT40
https://www.youtube.com/watch?v=SBv7a17ex0E
From: Forgotten Weapons, capandball