Offhand at 200 yards is WAY more difficult than shooting with a solid rest out to 800 or so.
I've made two fantastic shots and both were inside of 250 yards. One was offhand at a wounded running mulie at dark on the last day of the season and one was off high sticks at 250 on a big kudu. I was crazy buck-feverish on the kudu. We had been running to get ahead of them and they popped out of a tree line just before dark. Unsteady is a gross understatement. Somehow, magically, it all worked out.
My last bull elk was at 515 yards and my last three mulies were at 520, 540, and 420. I limit myself to 600 on deer if conditions are perfect. Elk are much bigger and I'm confident on them out to 800, but again this is with time to set up, get absolutely steady, read the wind, think about elevation, angle, temperature, and make a perfect shot with perfect trigger technique. Last year I passed on a buck that another guy shot later. He taped out at over 190 inches. He was at 600 yards, but it was gusty and I didn't have a great rest. We tried to close the distance but we got busted. That one haunts me a bit.
The mulie at 540 was, again, at dark on the last day. A little 3-point was bedded and all I could see was his head, so that's where I shot him. I had 15 minutes to set it up and was close enough to the truck I went and got my bags. My buddy thought it was pretty cool.
Banging steel routinely at 1000 does wonders for your confidence at 400.
Misses? Oh yeah - plenty. Only one or two recently though. These days I'm more likely to pass or wait for a high-percentage shot. The critters deserve it. The worst was on a waterbuck at 250. Whiffed it totally. My rest wasn't the best and I might have been a little excited. Luckily we found him again and I didn't miss the second time.