Re: big 7 or big 30
I think 1000-1200 is not only optimistic, it's also the absolute max. Max meaning having fire lapped at least once after severe throat wear and heat checking, and having it set it back at least once. Yes it's possible to maintain sub MOA for 1000+ rounds but it takes work. You can't expect to work up a load for a caliber like this and then fire 1000-1200 rounds with the same degree of accuracy or velocity for that load. There will be adjustments on powder charges and seating depths. That's without fire lapping or set backs. You will work up a load, love it then have to back off the powder. Then seat bullets further out. After a couple 2 or 3 times doing that, you'll fire lap it. Then set it back.
Having said all that, you won't have these problems to such a high degree if you run mild loads. Then you can reach your 1000-1200 round mark without as much trouble. However, if you do that, you're at 300 win mag levels anyway. the 300 WM will offer you as much if not a bit better life running at near max loads. You could save money on brass and powder.
If you run top end loads in a 30-338 LMI, the first couple inches of barrel crack severely and the throat gets rough within 75-200 rounds depending on how hard tou push it. When this happens you will be forced into reducing your loads to keep the pressure at safe levels. This is due to the added friction due to the severe heat checking and throat erosion. The other option is to fire lap the barrel with 1/2 the normal amount. This will clear things up for a while. Your throat will advance .010-.020 doing this on top of any advancement from firing.
Not trying to burst your bubble, just trying to show you the potential problems. If you run mild loads, you'll be ok. You can get in trouble in a hurry with these huge cases. Start low and work up slowly. Very slowly. It only takes a handful of 'hot' loads during development to kill these barrels.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.