I cannot help with specific regards to the 85 grain Barnes xlc in the .243, however, I have found out some general information about loading these bullets that I can pass along.
Barnes indicates in their loading manual that the bullets should be loaded a minimum of .050 back from touching the lans and grooves. Also, it was passed along to me that there are usually 'sweet spots' for accuracy when loaded .030"-.070", .110"-.150", and sometimes at .250" away from the bore.
I have a load with the .308 150g bullet in a contender that is very near the mentioned .250" dimension. With 2x scope, I get < 1.5" regularly. I think that with a more refined scope, I could get that down some more, and perhaps with a little tinkering with the load, it would come in a bit farther. I've only had a few trips to the range to work on this one.
I very good friend has several rifles set up with these bullets; uses nothing else for hunting. I sent him a diminuative, 200 yard group from my 22-250. He returned a slightly smaller (about .5" group from his 7mm STW. His was at 300 yards. He lives and hunts in Wyoming (long range shots usually), and is a retired Army sniper instructor. He is VERY particular about accuracy.
So I've seen that they can shoot well from some number of firearms. They seem to be a bit persnickity, and may not shoot well in all barrels, but the performance on the game end is superb, so I am working with them until I can't make them shoot how I want.
I hope this info helps in your quest.
Tapper
