I am probably going to be buying an AR receiver with an RB Precision parts kit and an A2 stock here in the next couple weeks, and I was wondering what I would have to get on the upper to accept 7.62x54R ammunition.
*pauses to pick liquid nails off of hand*
I know a 7.62 barrel, but would I be able to get a regular 7.62x39 bolt face to hold the casing, or would I have to have one custom made? I know mags could be a potential problem, but that wouldn't be too hard to get worked out.

I've been wanting to see this for ages, but there's some difficulties in doing so.

Ruskie 7.62 is .311, not .308 like American ammo.
You need a custom bolt face and barrel with matching throat and bore.
You might need to redesign the entire upper to accept the larger bolt and barrel.
You already mentioned getting magazines to accept the ammo.

This is what I was afraid of

Maybe if it does turn out possible a few people could get a manufacturer to do a quick run of barrels. If 10 people are willing to I can almost guarantee that they would be able to get a manufacturer to turn out a few. I might make a post on ar15.com's forums, and see if there is anyone there that might be able to get in contact with someone that could actually make this go through.

That would be outstanding, but I expect it would be prohibitively expensive, even for some of the high rollers at ARFCOM.

Someone seriously needs to design an affordable, reliable, semiauto in x54R that isn't a friggin' Dragunov clone.

It would look alright with a thumbhole though?
I never realized there was a demand for it though whats the point of this may I ask?
I think it could be ill fated as that AR that works with AK mags but jammed constantly due to stereotypically dirty russian ammo.

Err... what?

We're talking about an AR15, with custom magazines, and an upper receiver that shoots 7.62x54R, because it has a lot of bang and is dirt cheap (I get if for <13 cents). Don't quite sure what ar you're talking about with AK magazines, could you clarify or give me a link please?

The AK mag reference is most likely to the SR-47. There was also a SR-74. Limited 500 model production for SF in Afghanistan for the purpose of cave clearing utilizing abundant enemy ammunition and magazines.

Eh, who knows. Some rifles look gay with a thumbhole, some don't. Besides, if this is true to the AR name, then you should be able to swap out any stock on it and have it accept any typical AR stock/grip.

The only thing I would foresee this being ill fated for, is price. I know a LOT of people want a blaster for all the x54R they buy, save, and put in their Mosins. I've actually mentioned the idea before here.

Custom work is almost always ridiculously expensive, and this looks to be almost entirely custom. Even if you throw parts together that work safely, people want a AR in x54, not some mutant gun that shoots it.

Mass production lowers prices, and unless this project can be priced well from the start, it'll probably have the same fate as uppers like 6.8SPC or 6.5 Grendel. At least you have crazy cheap ammo going for you, those didn't.

Get a PSL for a fairly cheap 7.62X54R rifle.

It's not cheap, really, but if you want a semi auto in that cartridge it is by comparison.

54R is WAY TOO LONG for the AR magazine idiot.
plus its RIMMED.