Dave - I just did the same routine with the 50 cal (this is an older GM LRH barrel - still has the old iron sights not the fiber optic) I think I got this barrel back around '98. I got absoultely the same results.
I guess the hot soapy water wash/clear hot water rinse and bore butter method isn't so bad.
This rifle has been sitting since November and even after running the first drying patch after the hot water rinse, it came out clean.
So as far as my MLs, the only benefit I can see using MX products is the amount of fouling between shots. And I won't know that until I get them out to the range.