Before you give up on the Barnes you might want to change your cleaning pattern to more or less and see if that makes it close in. I only shoot a std 338WM but I worked up one load with barnes MRX 225gr at 3,000fps and I was cleaning the tube after every shot. Never got it to do what I was hoping for consistantly. Then,Got some Horney 185gr GMX Superformance ammo and a new scope and when alighning the scope shot 15 rounds W-O Cleaning and it started locking in. I'm up to 30 rounds and have not cleaned that ole girl since Nov 2010. The Barnes will fowl quicker than the GMX since it is softer copper. I don't know which caused my better performance, and it may be more than one:
Horney “?X” primer
Horney Superformance Powder
ZEISS Victory Diavari scope
or 4 of the above....................
Just a thought!