I have a Bartlein. It is a 26-inch 1:9 straight taper 5R with a Harrell 4-port brake. I shoot 240 grain Sierras at a bit under 2700 fps. Bartlein chambered it using their NSW reamer designed for Sierra 220s. The barrel is mounted on an old Remington long action, bedded into a McMillan A5 with Badger M5 bottom metal -- it has a magazine. Shooting from the magazine, it will shoot 0.5 to 0.6 MOA 5-shot groups at 100 all day with an occasional 0.4. I have one 0.3 group (but that was a fluke) and some 0.7s when I stopped paying attention to the wind. I have an 8-inch diameter 1/2-inch AR500 plate. Shooting prone at 500 meters, those long-ass bullets really bounce that plate around. I haven't tried it on my 6-inch plate yet. That barrel has about 900 rounds through it and it is still shooting. In my experience, every good round after 1,200 is a gift. I just found a place where I can put my 8-inch plate out past 1,000 meters and shoot at it. If I'm lucky, I might hit it once or twice. Its a 3-hour drive but I'm hoping for a bit of fun out there.
I have had a Schneider and several Harts on this gun. The Bartlein is the best of that bunch. I also own three Kreigers on other rifles. I have a Kreiger in 308 with a similar length and profile and it is also a shooter. When this barrel burns out, I will call both of those guys and take the first one who can deliver.
If you are looking at long range, I think you want heavy bullets. Heavy bullets are long so you need a tight twist. The 9-twist is right for those 240s, something else is probably good for 210 Bergers or 208 Amax. Settle on your bullet (or at least the general type and weight) and then talk to the barrel guys. They want you to be happy and they will give you good advice.
According to Brian Litz, those bullets are still going 1335 fps at 1400 yards. At that range, the up-click is about 40 MOA and the time of flight is about 2 seconds so I'm thinking that I could maybe hit a medium-sized building.
If you get a good barrel, the magic will be brass. I have some very good military brass with Winchester headstamps. I would be pleased to buy some more ... anyone? Bueller?