I firmly believe there is no such thing as an "accurate" bullet or an "inaccurate" bullet. Every guns has likes and dislikes. You may find that a particular gun "loves" XP3, and another one of the same make may "hate" them.
I have seen far too many instances where a particular load in one gun shoots very well, but the very same load, down to the 1/10th of a grain of powder, shoots poorly in another gun. Does that make the bullet "accurate" or "inaccurate"?
I believe it is a mistake to conclude that just because a particular bullet in a particular load does not shoot well in certain guns, that it is inherently inaccurate. The same bullet with a different powder, or different primer, or different OAL may shoot very well in the same gun. Then again, it may not. You just have to ask your rifle what it likes and obey its wishes...