.338 Federal in an AR, maybe?

So I stumbled upon a DPMS pattern stripped upper for a good price, and am trying to decide the direction I'd like to go with the rest of it. Looking at barreling it for the .338 Federal possibly. Wondering who here has experience using that cartridge, and why you might choose it over .308?

From what I've been able to figure out, its basically a bit more punch in the same package. Do those performance gains continue past 500yrs? Past 1000? From some I've read, its nice at "intermediate" ranges, but starts to loose its luster much like the .308 once you really stretch it out. Makes sense, given the parent case, but curious about personal experiences.

Hand loads for it? Not sure what the action can handle on these rifles.... is there a generally agreed upon max bullet weight like that toted for the M14?

Advice on a barrel source? I've seen a few. Some are just the barrel, some are barrel/bolt combos, for a sure bet headspace I assume. I haven't picked up a BCG for it yet. Actually, all thats on the way is the Upper (charging handle/dust cover/ and FA too) and some Pmags so far.