Funk
I can't be sure what you call a "bug hole" at 100. If it is .300 to ,400 at 100, (a realistic goal for a 223), and .800 at 200, then that is about right.
Most Benchrest Shooters attribute verticle to tune. But, if it is shooting nice round holes at 100, and lots of verticle at 200, then you might be the victim of conditions. Intense tail and head winds will drive bullets up and down, depending upon the topography of the range. You just about have to be able to anylize the situation at the moment it happens to get an idea.
It is difficult to anylize why things do what they do without actually shooting the Rifle. If I am sitting at the bench, and my Rifle is acting goofy, I can pretty well figure things out, and find out what is going on.
I am NOT one of those shooters who believe that there is a 100 and 200 yard tune, or at least as it pertains to Benchrest Rifles. If a Rifle will agg at 100, it should at 200, and vice-versa.
That leaves an outside source as the cause of the problem. That means conditions.........jackie