Blucollar,
i have the Huntsman ML and .243 combination rifle. i went to the range, shot 20 rounds of .243 and 10 Powerbelts with out cleaning the barrels, breech or reciever with out any problems whats so ever. the ML does dirty the reciever where the barrel breech rests but not enough to damage or hinder function. when i returned home, a descent cleaning was all that was needed. i dont see any long term problems like Tim said, threre are multitudes of these out there being used every season.
If your thinking of getting the ML barrel and getting it fitted to your ultra, go for it, its a real nice package to have at your disposal.
Glenn