If your willing to lay down the money, get a SL8. Or a G36. Do the longer barrel and foregrip conversion.
I've made custom sniper mags for my G36C. I'll show you a picture later on.
You can probably get a mini tripod for that.
Get a longer 6.04 inner barrel. Get your gearbox upgraded to shoot around 400fps. There you go, a perfect sniper gun.
M14 has a v2 gearbox. You're going to have to replace the mechbox a lot sooner if you have it upgraded. And the v2 stock gearbox isn't as upgradable as the V3 stock.
So if you want something thats easy to work on, does full auto and is very accurate I'd go for a G36 variant.
When I think of the M14 I think of it having a M203 on it. Not a sniper gun.
One reason why I don't like bolt action is because it's too damn slow. Your in the middle of the game and you see all your teammates running around, while your just campin your ass out trying to get a target. It's not as fun.
For the price you pay for a good bolt action you can get a highly upgraded AEG with all the goodies on it.
Thats why I suggest an upgraded AEG. You have fun using your gun as a sniper and a primary AEG.