As mentioned, a rough bore will exponentially increase fouling! Also (as mentioned), the long, generally accepted rule when shooting Barnes Bullets, is to thoroughly clean the bore of any residual fouling from other bullets.
I've used Barnes Bullets since the early '90's ( the original X Bullet), and never had a fouling issue.....though, I was running them through a "match grade" barrel. Once having used them, I never had a desire to change.....except to change to newer Barnes Bullets as their technology progressed!
I had a friend that tried the originals, and got hideous groups. Once I "finally" convinced him to polish his bore, he got much better grouping. It was close to match performance, but adequate for hunting big game @ ranges under 400 yards. Slightly off topic, his first and only elk was taken that year. A "single" X Bullet from a 25-06, took the biggest bodied bull, I've ever seen. He also got an exit, which the Barnes are recognized for.....and loved by many! memtb