I hate to disagree but..........
Monolithic copper bullets (Barnes, Grooves, etc) foul like crazy.
Conventional lead core jacketed bullets have a thin but hard copper jacket. The lead core easily allows the bullet to obturate as it is forced into the rifling and the jacket can, therefore, be harder and resist wiping off in the bore.
The solid copper bullets MUST be made from a softer copper in order to allow them to obturate sufficiently. The down side to this softer copper is bore fouling. This can be a significant problem in a rough factory bore. This is why Barnes sells CR-10, a very powerful copper cleaner. Just smelling the stuff makes your head spin. If used improperly, it can damage the bore.
The newer Barnes TSX bullets, with the bearing rings, are designed to reduce the bullet body to bore contact area, thus, reducing copper fouling and chamber pressure. How much reduction may depend on how smooth or rough the bore is. It does appear to be beneficial to accuracy, and the TSX is finding a home in many guns that could not shoot regular X bullets.
There are so many other quality, accurate, premium bullets out there now that it hardly seems worth the time, trouble and expense to use solid copper bullets. However, if you just have to have the maximum amount of penetration possibe, the solid copper bullets may just be the ticket.
Just my 2 cents - Milage may vary
VH