What kind of group can you shoot at 200 yards ? Do you have a rangefinder ?
Do you chronograph your loads ? Do you understand the effect of wind and can you read it ? Actually the wind is what will probably get you.
If a man can shoot a 2 inch group at 200 yards he doesn't have to practice at 400 yards to make that shot. There are plenty of programs that will tell you where you will be at longer ranges accurately enough for elk size game.