I didnt realize it was you, we have played together on several occasions, for that jeep assignments you have to dedicate the whole round, using the DPV jeep every time you spawn, it will be really frustrating(I have tried it)
As for sniper, you can get easy sniper shots in Metro but the distance in metro doesn't go beyond 250-290 m I think
If you want to get the 350m headshot, try Caspian Border, go the "Hilltop"(D flag in Conquest Large) from there you can snipe enemies coming from the RU base(towards B flag,again in CQ large), also you can take out enemies coming from E flag
As for rifle, for long range M98B is the gold standard, with a 8x or 12x scope(depending on your taste), using a bipod to stabilse is good, but I personally think going prone for sniping is not good, you become a easier target, so straight pull bolt can used, never use laser, it reveals your positions