Like I said, if there's enough shank to cut a new tenon a 700 barrel will work.

My favorite Remington contours don't have enough shank but then I prefer sporter or lighter contour barrels over the truck axles.

The only savings gleaned from using a used 700 barrel is the difference in price of a new barrel over what you pay for the used one.
You still have all the same machining to do to a used barrel as you would a new one and you still have a used barrel.

False economy unless the used barrels are nearly free IMO.