I'm starting to see a pattern when it comes to Barnes X bullets, pretty much across the board when it comes to caliber... I started trying them when they first hit the market, and have had outstanding accuracy with virtually all my rifles. Especially my .45-70... Now, here is what I have noticed. I DO NOT LOAD HOT. In fact, for most of my hunting, since it's is all close range, I use a term that I have more or less coined. I call it 100 yard loads. I load most of my muzzle velocities to that which you would normally find out at around 100 yards. For wild boar hunting using 180 grain bullets, this results in a muzzle velocity of around 2400 fps or just a bit more.
Now, without question, some rifles just will not shoot the Barnes X no matter what you do, but here is my theory. The jacketed lead core bullets, which of course make up most of the premium bullets have the hardest jackets, while the copper used in the Barnes X bullets is somewhat softer. Also, of course, lead is softer yet. The lead core jacketed bullets will obturate (slug) inside the barrel, and thereby conform to differences in actual barrel dimensions. However, the all copper Barnes X bullet will not do this, and needs a better "match" or fit to begin with. Over the years, I have noticed that the guys who have emailed me, or posted on my forum about having accuracy problems, almost without fail, were loading very hot... We all know that cast lead bullets will only work properly up to a certain velocity. Beyond that, accuracy will fall off dramatically, and lead fouling goes way up... I'm thinking that perhaps, slowing down the Barnes X bullets a bit may be at least in part, an answer to accuracy problems. They don't slug and conform to the barrel, and if pushed too fast, I am thinking that perhaps the "skid" down the barrel, and don't get the proper spin... They also copper foul badly if pushed too fast... Just a thought, but I am starting to think there is something to this... since again, I load to modest velocities, and have never had accuracy problems. One note: Obviously, depending on the weight of the bullet, you are going to have to load to a velocity that will stabilize the bullet, but this will not be anywhere near MAX velocity...