I have been shooting quite a bit lately with the Barnes TSX. I have been surprised how little they are copper fouling the barrel. Far better than the old X bullet.
Probably shot +80 rounds this past weekend and ran some copper/powder foam cleaner through the bore. Very little if any blue coloring showed up on the patches afterwards.
Seems far more accurate as well. Quite an improvement.

I've had the same experience with the TSX's compared to the old X bullets. The TSX's seem to be much more consistent from box to box as compared to the old X bullets as well. I have switched several rifles over to them including 223, 25-06, 270Wby, 30-378Wby, 375H&H, 416 Rem and Rigby, 458's and 470NE.

Ed

I use the TSX in my 6.8 & 30-378, but it's awful hard to break from those nosler partitions in my bigger guns, superstitious after all these years.

I get almost 50 shots in my .30-06 before there's enough fouling to degrade accuracy and require cleaning. The relief grooves really seem to work.

LWD

Ye the TSX is a HUGE improvement on the old X bullets in ALL ways including accuracy & higher velocity. Cleaner barrel is a big bonus.

They are 1 thou smaller than nominal diameter apart from the driving bands.