I have no experience with Sassen barrels and the likes, only factory hammer forged barrels.To illustrate my point in an earlier reply In this thread, I went out with a brand new and fresh back from proof rifle this morning to zero and do some load development
Fired a total of 30 rounds in an XC - Sassen cut rifled barrel
Velocity up there in the accuracy node 3000 fps plus and no sign of excess pressure whatsoever
Once home the barrel cleaned out using 5 patches of carbon cleaner (Boretech) and 4 patches of Cu cleaner (Boretech)
Regardless of the state of these barrels, patches only will only clean out superficial crud. I am not a supporter of cleaning down to bare steel on a regular cleaning but using a bronze brush is a must in my experience. Anything else is just eyewash.