I see that 7 Rem is suppedly offered in 175 grain but I'm not seeing this in stock anywhere. Is this configuration only for reloaders?
175s certainly exist. Federal lists 3 loads with a 175gr bullet, a Fusion, a PowerShok, and a Trophy Bonded Bear Claw. Only the Fusion is listed as currently available though, lots of products from federal have been put on hold while they try to catch up with demand for more common stuff.
I know I've seen Winchester Super X in 175gr at Walmart, as well as Rem Corelokt.... but none of these budget- oriented options are going to give you the kind of accuracy required for 500+yds, at least not in my experience with them.