The gents in the previous posts are dead on. My hunting partner, my father & I all shoot Barnes bullets (for hunting) & i've learned the fouling lesson the hard way... several times
While reading your post I can't help but wonder; you stated that your rifle shot great with 100grn "conventional" bullets... Did you thoroughly clean the bore before shooting the Barnes? If not, I guarantee
your bore is rediculously fouled (ask me how I know).
As the two bullets use different hardnesses of copper & they actually can/do layer on top of each other. The "conventional" bullets being harder, they can actually help to strip more copper from your Barnes leading to very bad fouling.
You can also try the 85grn TSX, which has a great reputation as well.
Give us the "skinney" on your reloads-