Just seeing this now, but before changing out the barrel I’d check the gun out overall for stuff like loose action screws, barrel to stock contact, a crown that looks like a 5 year old Chinese kid did it, etc. A 14” group at 800 yards is reasonable for grandpa’s old .270, but most modern rifles will shoot sub MOA, especially in cartridges that tend to be accurate like Hornady’s 143 ELD-X in 6.5.
This is all assuming it shoots similar groups with somebody else behind the trigger and it’s not super windy.