54r AR build questions

[Purdune]

Howdy,
Never built a gun though I own several and am familiar with the operation of several design types. I'm also handy with tools and though today my main tool is a keyboard, I still retain calluses on my hands. What I'd like to do is build my own AR in 7.62x54r. I like the round, can buy cheap for plinking, and make my own match loads. I'd rather piston rather than gas operation. I know the barrel/chamber will have to be special order/made. Just wondering what off the shelf parts I can use/modify. For instance can I get an AR-10 lower, upper, and bolt? If so what modifications can I do and what would I need a gun smith for?

What I'd like out of the rifle.
Accuracy, 2 to 3 MOA. Looking to be the guy that takes out people while the platoon maneuvers and pins. (LOL in theory only!)
Reliability, not drop it in the mud however that would be nice. I break down and clean everything after each use. Doesn't mean I want it to fail with a little grime in it. Will want chamber chromed and what not.
Cheap, yeah ok I know. This is a special build and I want it to work really well that's money. I'm not looking to go to go to Red Jacket and have everything hand built to NASA tolerances. Looking for off the shelf where I can, what I can modify myself, and last what I've got to have a gun smith make/modify.