Re: Junk Yard .308 build
I have a 28" 6mm Rem built on a Rem 700 Long Action which is a decent 1000+ yard target rifle. All the parts were bought on ebay (before they banned most gun parts). The action was off a beat up pawn shop 700 sporter. If you want to shoot VLD bullets from just about any of the "short action" cartridges, using a long or at least mid (30-06) length action is reasonable, and necessary to feed though a magazine. . It removes most of the constraints on seating depth. Brass over 2" long is very cramped in a 2.8" magazine with VLDs. Certainly if I was building a rifle with any of the SAUM or WSM cartridges I'd use long action.
In my opinion the Rem 700 long action is too short to work well with the long magnums like the Rem Ultras. 2.8" brass is cramped with VLDs in a 3.6" or even 3.8" actions.
You can call that a "junk yard" build if you want, but I'd expect it to work well. That's hardly a junk barrel. Where you get parts isn't the issue. It's how well they the match the cartridge and how well they're assembled.